Add spinner + better attribution in REPL. Several changes to the REPL,
 - better attribution of Emscripten (we talked about it but didn't do the change): the gif below doesn't include this change.
 - Attribute for the Jquery Terminal: I added a clickable grey link on the right top of the REPL. On mobile, I think it should be OK, since we don't really scale text currently, so there is still enough space to display it. There was an issue that this was the only text that was displayed while loading.  
 - So I ended up adding a spinner for loading as well. Potentially we could re-use it for indicating that a package is being loaded as it's continuously running in the background, we just need to put it in the foreground with `z-index: 2` and hide it again after the package is loaded.
 
![Peek 2022-05-28 12-05](https://user-images.githubusercontent.com/630936/170820858-7f2ad6dc-0eb5-4f4e-9920-b59cfe8044e9.gif)


<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <script src="https://cdn.jsdelivr.net/npm/jquery"></script>
    <script src="https://cdn.jsdelivr.net/npm/jquery.terminal@2.32.0/js/jquery.terminal.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/jquery.terminal@2.23.0/js/unix_formatting.min.js"></script>
    <link
      href="https://cdn.jsdelivr.net/npm/jquery.terminal@2.32.0/css/jquery.terminal.min.css"
      rel="stylesheet"
    />
    <script src="{{ PYODIDE_BASE_URL }}pyodide.js"></script>
    <style>
      .terminal {
        --size: 1.5;
        --color: rgba(255, 255, 255, 0.8);
      }
    </style>
  </head>
  <body>
    <script>
      "use strict";
      function sleep(s) {
        return new Promise((resolve) => setTimeout(resolve, s));
      }

      async function main() {
        let term;
        globalThis.pyodide = await loadPyodide({
          stdin: () => {
            let result = prompt();
            echo(result);
            return result;
          },
        });
        let namespace = pyodide.globals.get("dict")();
        pyodide.runPython(
          `
            import sys
            from pyodide import to_js
            from pyodide.console import PyodideConsole, repr_shorten, BANNER
            import __main__
            BANNER = "Welcome to the Pyodide terminal emulator 🐍\\n" + BANNER
            pyconsole = PyodideConsole(__main__.__dict__)
            import builtins
            async def await_fut(fut):
              res = await fut
              if res is not None:
                builtins._ = res
              return to_js([res], depth=1)
            def clear_console():
              pyconsole.buffer = []
        `,
          { globals: namespace }
        );
        let repr_shorten = namespace.get("repr_shorten");
        let banner = namespace.get("BANNER");
        let await_fut = namespace.get("await_fut");
        let pyconsole = namespace.get("pyconsole");
        let clear_console = namespace.get("clear_console");
        const echo = (msg, ...opts) =>
          term.echo(
            msg.replace("]]", "&rsqb;&rsqb;").replace("[[", "&lsqb;&lsqb;"),
            ...opts
          );
        namespace.destroy();

        let ps1 = ">>> ",
          ps2 = "... ";

        async function lock() {
          let resolve;
          let ready = term.ready;
          term.ready = new Promise((res) => (resolve = res));
          await ready;
          return resolve;
        }

        async function interpreter(command) {
          let unlock = await lock();
          term.pause();
          // multiline should be split (useful when pasting)
          for (const c of command.split("\n")) {
            let fut = pyconsole.push(c);
            term.set_prompt(fut.syntax_check === "incomplete" ? ps2 : ps1);
            switch (fut.syntax_check) {
              case "syntax-error":
                term.error(fut.formatted_error.trimEnd());
                continue;
              case "incomplete":
                continue;
              case "complete":
                break;
              default:
                throw new Error(`Unexpected type ${ty}`);
            }
            // In JavaScript, await automatically also awaits any results of
            // awaits, so if an async function returns a future, it will await
            // the inner future too. This is not what we want so we
            // temporarily put it into a list to protect it.
            let wrapped = await_fut(fut);
            // complete case, get result / error and print it.
            try {
              let [value] = await wrapped;
              if (value !== undefined) {
                echo(
                  repr_shorten.callKwargs(value, {
                    separator: "\n<long output truncated>\n",
                  })
                );
              }
              if (pyodide.isPyProxy(value)) {
                value.destroy();
              }
            } catch (e) {
              if (e.constructor.name === "PythonError") {
                const message = fut.formatted_error || e.message;
                term.error(message.trimEnd());
              } else {
                throw e;
              }
            } finally {
              fut.destroy();
              wrapped.destroy();
            }
          }
          term.resume();
          await sleep(10);
          unlock();
        }

        term = $("body").terminal(interpreter, {
          greetings: banner,
          prompt: ps1,
          completionEscape: false,
          completion: function (command, callback) {
            callback(pyconsole.complete(command).toJs()[0]);
          },
          keymap: {
            "CTRL+C": async function (event, original) {
              clear_console();
              term.enter();
              echo("KeyboardInterrupt");
              term.set_command("");
              term.set_prompt(ps1);
            },
            TAB: (event, original) => {
              const command = term.before_cursor();
              // Disable completion for whitespaces.
              if (command.trim() === "") {
                term.insert("\t");
                return false;
              }
              return original(event);
            },
          },
        });
        window.term = term;
        pyconsole.stdout_callback = (s) => echo(s, { newline: false });
        pyconsole.stderr_callback = (s) => {
          term.error(s.trimEnd());
        };
        term.ready = Promise.resolve();
        pyodide._api.on_fatal = async (e) => {
          term.error(
            "Pyodide has suffered a fatal error. Please report this to the Pyodide maintainers."
          );
          term.error("The cause of the fatal error was:");
          term.error(e);
          term.error("Look in the browser console for more details.");
          await term.ready;
          term.pause();
          await sleep(15);
          term.pause();
        };
      }
      window.console_ready = main();
    </script>
  </body>
</html>

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <script src="https://cdn.jsdelivr.net/npm/jquery"></script>
    <script src="https://cdn.jsdelivr.net/npm/jquery.terminal@2.32.0/js/jquery.terminal.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/jquery.terminal@2.23.0/js/unix_formatting.min.js"></script>
    <link
      href="https://cdn.jsdelivr.net/npm/jquery.terminal@2.32.0/css/jquery.terminal.min.css"
      rel="stylesheet"
    />
    <script src="{{ PYODIDE_BASE_URL }}pyodide.js"></script>
    <style>
      .terminal {
        --size: 1.5;
        --color: rgba(255, 255, 255, 0.8);
      }
      body {
        background-color: black;
      }
      #jquery-terminal-logo {
        color: white;
        border-color: white;
        position: absolute;
        top: 7px;
        right: 18px;
        z-index: 2;
      }
      #jquery-terminal-logo a {
        color: gray;
        text-decoration: none;
        font-size: 0.7em;
      }
      #loading {
        display: inline-block;
        width: 50px;
        height: 50px;
        position: fixed;
        top: 50%;
        left: 50%;
        border: 3px solid rgba(172, 237, 255, 0.5);
        border-radius: 50%;
        border-top-color: #fff;
        animation: spin 1s ease-in-out infinite;
        -webkit-animation: spin 1s ease-in-out infinite;
      }

      @keyframes spin {
        to {
          -webkit-transform: rotate(360deg);
        }
      }
      @-webkit-keyframes spin {
        to {
          -webkit-transform: rotate(360deg);
        }
      }
    </style>
  </head>
  <body>
    <div id="jquery-terminal-logo">
      <a href="https://terminal.jcubic.pl/">jQuery Terminal</a>
    </div>
    <div id="loading"></div>
    <script>
      "use strict";
      function sleep(s) {
        return new Promise((resolve) => setTimeout(resolve, s));
      }

      async function main() {
        let term;
        globalThis.pyodide = await loadPyodide({
          stdin: () => {
            let result = prompt();
            echo(result);
            return result;
          },
        });
        let namespace = pyodide.globals.get("dict")();
        pyodide.runPython(
          `
            import sys
            from pyodide import to_js
            from pyodide.console import PyodideConsole, repr_shorten, BANNER
            import __main__
            BANNER = "Welcome to the Pyodide terminal emulator 🐍\\n" + BANNER
            pyconsole = PyodideConsole(__main__.__dict__)
            import builtins
            async def await_fut(fut):
              res = await fut
              if res is not None:
                builtins._ = res
              return to_js([res], depth=1)
            def clear_console():
              pyconsole.buffer = []
        `,
          { globals: namespace }
        );
        let repr_shorten = namespace.get("repr_shorten");
        let banner = namespace.get("BANNER");
        let await_fut = namespace.get("await_fut");
        let pyconsole = namespace.get("pyconsole");
        let clear_console = namespace.get("clear_console");
        const echo = (msg, ...opts) =>
          term.echo(
            msg.replace("]]", "&rsqb;&rsqb;").replace("[[", "&lsqb;&lsqb;"),
            ...opts
          );
        namespace.destroy();

        let ps1 = ">>> ",
          ps2 = "... ";

        async function lock() {
          let resolve;
          let ready = term.ready;
          term.ready = new Promise((res) => (resolve = res));
          await ready;
          return resolve;
        }

        async function interpreter(command) {
          let unlock = await lock();
          term.pause();
          // multiline should be split (useful when pasting)
          for (const c of command.split("\n")) {
            let fut = pyconsole.push(c);
            term.set_prompt(fut.syntax_check === "incomplete" ? ps2 : ps1);
            switch (fut.syntax_check) {
              case "syntax-error":
                term.error(fut.formatted_error.trimEnd());
                continue;
              case "incomplete":
                continue;
              case "complete":
                break;
              default:
                throw new Error(`Unexpected type ${ty}`);
            }
            // In JavaScript, await automatically also awaits any results of
            // awaits, so if an async function returns a future, it will await
            // the inner future too. This is not what we want so we
            // temporarily put it into a list to protect it.
            let wrapped = await_fut(fut);
            // complete case, get result / error and print it.
            try {
              let [value] = await wrapped;
              if (value !== undefined) {
                echo(
                  repr_shorten.callKwargs(value, {
                    separator: "\n<long output truncated>\n",
                  })
                );
              }
              if (pyodide.isPyProxy(value)) {
                value.destroy();
              }
            } catch (e) {
              if (e.constructor.name === "PythonError") {
                const message = fut.formatted_error || e.message;
                term.error(message.trimEnd());
              } else {
                throw e;
              }
            } finally {
              fut.destroy();
              wrapped.destroy();
            }
          }
          term.resume();
          await sleep(10);
          unlock();
        }

        term = $("body").terminal(interpreter, {
          greetings: banner,
          prompt: ps1,
          completionEscape: false,
          completion: function (command, callback) {
            callback(pyconsole.complete(command).toJs()[0]);
          },
          keymap: {
            "CTRL+C": async function (event, original) {
              clear_console();
              term.enter();
              echo("KeyboardInterrupt");
              term.set_command("");
              term.set_prompt(ps1);
            },
            TAB: (event, original) => {
              const command = term.before_cursor();
              // Disable completion for whitespaces.
              if (command.trim() === "") {
                term.insert("\t");
                return false;
              }
              return original(event);
            },
          },
        });
        window.term = term;
        pyconsole.stdout_callback = (s) => echo(s, { newline: false });
        pyconsole.stderr_callback = (s) => {
          term.error(s.trimEnd());
        };
        term.ready = Promise.resolve();
        pyodide._api.on_fatal = async (e) => {
          term.error(
            "Pyodide has suffered a fatal error. Please report this to the Pyodide maintainers."
          );
          term.error("The cause of the fatal error was:");
          term.error(e);
          term.error("Look in the browser console for more details.");
          await term.ready;
          term.pause();
          await sleep(15);
          term.pause();
        };
      }
      window.console_ready = main();
    </script>
  </body>
</html>
