This is the mirror image of #2170.

### Checklists

<!-- Note on checklists:
     If you think some of these steps are not necessary for your PR,
     just remove those checkboxes, or mark them as checked. Otherwise,
     if some checkboxes are left unmarked, we might assume that your PR
     is not ready to be merged and we might keep you waiting -->

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [x] Add new / update outdated documentation

Add `default_converter` argument to `to_js` and `toJs`. This is the mirror image of #2170.

### Checklists

<!-- Note on checklists:
     If you think some of these steps are not necessary for your PR,
     just remove those checkboxes, or mark them as checked. Otherwise,
     if some checkboxes are left unmarked, we might assume that your PR
     is not ready to be merged and we might keep you waiting -->

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [x] Add new / update outdated documentation

# Sphinx-Pyodide

This package is a special sphinx extension for Pyodide's documentation.
The three separate files do three unrelated tasks:

## packages

Adds a custom directive which makes a table of the Pyodide packages

## lexers

Adds custom pyodide Pygments lexers that provides syntax highlighting for
Javascript with embedded Python code, and for HTML with embedded Javascript that
itself contains embedded Python.

e.g., in

```pyodide
await pyodide.loadPackage(numpy);
pyodide.runPython(`
    def f(y):
        return y + ${x}
    f(7)
`);
```

the code inside of `pyodide.runPython` is highlighted as Python, the other code
is highlighted as Javascript. Similarly with `html-pyodide`:

```html-pyodide
<div></div>
<script type="text/javascript">
console.log(pyodide.runPython(`
    import sys
    sys.version
`));
</script>
```

## jsdoc

This extends `sphinx-js` for our purposes. This contains a mix of missing
features that could ideally be upstreamed into `sphinx-js` and custom code that
can't be upstreamed.

### TsAnalyzer monkey patches

We monkey patch `TsAnalyzer._type_name` to fill in formatting of types that were
left as TODOs by `sphinx-js` (this could probably be upstreamed).

We monkey patch `TsAnalyzer._convert_node` to fix two crashes (could be
upstreamed) and to turn a destructured object argument into a list of argument docs:

```js
/**
* @param options
*/
function f({x , y } : {
    /** The x value */
    x : number,
    /** The y value */
    y : string
}){ ... }
```

should be documented like:

```
options.x (number) The x value
options.y (number) The y value
```

### `js:function`

We update the `js:function` directive to display `async` in front of async
functions.

### `PyodideAnalyzer`

We compose `TsAnalyzer` into `PyodideAnalyzer`. This prunes out private
functions, marks functions as `async` so we can display `async` in front of
them, and organizes functions into our three categories:

- `globalThis`: globaly exposed functions
- `pyodide`: pyodide APIs
- `PyProxy`: `PyProxy` APIs

It also classifies them into three types: function, class, or attribute so we
can separate them out in the summary.

### js-autodoc

`sphinx-js` doesn't include full recursive layout features by default. This adds
a `js-doc-summary` directive and a `js-doc-content` directive. `js-doc-summary`
makes a summary table for any category (`globalThis`, `pyodide` or `PyProxy`)
and `js-doc-content` formats the main documentation content. These are used in
`js-api.md`. A lot of this code is similar to the `autosummary` package, but
there are enough differences that it was easier to copy the code in.

## autodoc_submodules

This makes autodoc recursively document submodules, mixed in with the top level
docs. For instance, `pyfetch` is defined in `pyodide.html`. This adds an entry
called `http.pyfetch` to the list of documented APIs for `pyodide`.

# Sphinx-Pyodide

This package is a special sphinx extension for Pyodide's documentation.
The three separate files do three unrelated tasks:

## packages

Adds a custom directive which makes a table of the Pyodide packages

## lexers

Adds custom pyodide Pygments lexers that provides syntax highlighting for
Javascript with embedded Python code, and for HTML with embedded Javascript that
itself contains embedded Python.

e.g., in

```pyodide
await pyodide.loadPackage(numpy);
pyodide.runPython(`
    def f(y):
        return y + ${x}
    f(7)
`);
```

the code inside of `pyodide.runPython` is highlighted as Python, the other code
is highlighted as Javascript. Similarly with `html-pyodide`:

```html-pyodide
<div></div>
<script type="text/javascript">
console.log(pyodide.runPython(`
    import sys
    sys.version
`));
</script>
```

## jsdoc

This extends `sphinx-js` for our purposes. This contains a mix of missing
features that could ideally be upstreamed into `sphinx-js` and custom code that
can't be upstreamed.

### TsAnalyzer monkey patches

We monkey patch `TsAnalyzer._type_name` to fill in formatting of types that were
left as TODOs by `sphinx-js` (this could probably be upstreamed).

We monkey patch `TsAnalyzer._convert_node` to fix two crashes (could be
upstreamed) and to turn a destructured object argument into a list of argument docs:

```js
/**
* @param options
*/
function f({x , y } : {
    /** The x value */
    x : number,
    /** The y value */
    y : string
}){ ... }
```

should be documented like:

```
options.x (number) The x value
options.y (number) The y value
```

### `js:function`

We update the `js:function` directive to display `async` in front of async
functions.

### `PyodideAnalyzer`

We compose `TsAnalyzer` into `PyodideAnalyzer`. This prunes out private
functions, marks functions as `async` so we can display `async` in front of
them, and organizes functions into our three categories:

- `globalThis`: globaly exposed functions
- `pyodide`: pyodide APIs
- `PyProxy`: `PyProxy` APIs

It also classifies them into three types: function, class, or attribute so we
can separate them out in the summary.

### js-autodoc

`sphinx-js` doesn't include full recursive layout features by default. This adds
a `js-doc-summary` directive and a `js-doc-content` directive. `js-doc-summary`
makes a summary table for any category (`globalThis`, `pyodide` or `PyProxy`)
and `js-doc-content` formats the main documentation content. These are used in
`js-api.md`. A lot of this code is similar to the `autosummary` package, but
there are enough differences that it was easier to copy the code in.

## autodoc_submodules

This makes autodoc recursively document submodules, mixed in with the top level
docs. For instance, `pyfetch` is defined in `pyodide.html`. This adds an entry
called `http.pyfetch` to the list of documented APIs for `pyodide`.
