No directory exists at 'electrum/www'
Following the docs on [How to accept Bitcoin on a website using Electrum](https://electrum.readthedocs.io/en/latest/merchant.html#how-to-accept-bitcoin-on-a-website-using-electrum) fails at rendering the payserver due to the [www](https://github.com/spesmilo/electrum/blob/7698ab4ccb11451a1964ac03e00e258f431c2a41/electrum/daemon.py#L341) [directory](https://github.com/spesmilo/electrum-http) missing.

Interestingly, extracting [Electrum-4.0.9.tar.gz](https://download.electrum.org/4.0.9/Electrum-4.0.9.tar.gz), the `electrum-http` contents and be found in `Electrum-4.0.9/electrum/www`

Steps to reproduce:
```bash
/Applications/Electrum.app/Contents/MacOS/run_electrum -o setconfig payserver_address localhost:2029
/Applications/Electrum.app/Contents/MacOS/run_electrum daemon -v=warning
```
Output
```
I | logging | Electrum version: 4.0.9 - https://electrum.org - https://github.com/spesmilo/electrum
I | logging | Python version: 3.7.9 (default, Sep 11 2020, 17:18:37)
[Clang 11.0.0 (clang-1100.0.33.17)]. On platform: Darwin-19.6.0-x86_64-i386-64bit
I | logging | Logging to file: None
I | logging | Log filters: verbosity 'warning', verbosity_shortcuts ''
E | daemon.PayServer | Exception in run: ValueError("No directory exists at '/Applications/Electrum.app/Contents/Resources/electrum/www'")
Traceback (most recent call last):
  File "aiohttp/web_urldispatcher.py", line 553, in __init__
ValueError: Not a directory

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "electrum/util.py", line 1056, in wrapper
  File "electrum/daemon.py", line 341, in run
  File "aiohttp/web_app.py", line 333, in add_routes
  File "aiohttp/web_urldispatcher.py", line 1213, in add_routes
  File "aiohttp/web_routedef.py", line 100, in register
  File "aiohttp/web_urldispatcher.py", line 1126, in add_static
  File "aiohttp/web_urldispatcher.py", line 555, in __init__
ValueError: No directory exists at '/Applications/Electrum.app/Contents/Resources/electrum/www'
```

Similar error on Linux for a pip installed electrum instance
```
I | logging | Electrum version: 4.0.9 - https://electrum.org - https://github.com/spesmilo/electrum
I | logging | Python version: 3.6.9 (default, Jan 26 2021, 15:33:00)
[GCC 8.4.0]. On platform: Linux-5.9.6-x86_64-linode139-x86_64-with-Ubuntu-18.04-bionic
I | logging | Logging to file: None
I | logging | Log filters: verbosity 'warning', verbosity_shortcuts ''
E | daemon.PayServer | Exception in run: ValueError("No directory exists at '/root/.local/lib/python3.6/site-packages/electrum/www'",)
Traceback (most recent call last):
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_urldispatcher.py", line 553, in __init__
    raise ValueError("Not a directory")
ValueError: Not a directory

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/root/.local/lib/python3.6/site-packages/electrum/util.py", line 1056, in wrapper
    return await func(*args, **kwargs)
  File "/root/.local/lib/python3.6/site-packages/electrum/daemon.py", line 341, in run
    app.add_routes([web.static(root, os.path.join(os.path.dirname(__file__), 'www'))])
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_app.py", line 333, in add_routes
    return self.router.add_routes(routes)
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_urldispatcher.py", line 1213, in add_routes
    registered_routes.extend(route_def.register(self))
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_routedef.py", line 100, in register
    resource = router.add_static(self.prefix, self.path, **self.kwargs)
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_urldispatcher.py", line 1126, in add_static
    append_version=append_version,
  File "/root/.local/lib/python3.6/site-packages/aiohttp/web_urldispatcher.py", line 555, in __init__
    raise ValueError(f"No directory exists at '{directory}'") from error
ValueError: No directory exists at '/root/.local/lib/python3.6/site-packages/electrum/www'
```
diff --git a/setup.py b/setup.py
index fc5d9c71a..efcd5dd0f 100755
--- a/setup.py
+++ b/setup.py
@@ -79,17 +79,10 @@ setup(
     package_dir={
         'electrum': 'electrum'
     },
-    package_data={
-        '': ['*.txt', '*.json', '*.ttf', '*.otf', '*.csv'],
-        'electrum': [
-            'wordlist/*.txt',
-            'locale/*/LC_MESSAGES/electrum.mo',
-            'lnwire/*.csv',
-        ],
-        'electrum.gui': [
-            'icons/*',
-        ],
-    },
+    # Note: MANIFEST.in lists what gets included in the tar.gz, and the
+    # package_data kwarg lists what gets put in site-packages when pip installing the tar.gz.
+    # By specifying include_package_data=True, MANIFEST.in becomes responsible for both.
+    include_package_data=True,
     scripts=['electrum/electrum'],
     data_files=data_files,
     description="Lightweight Bitcoin Wallet",
['setup.py']