Update docs to remove reference to flask run

[willthames]

According to #894, flask run no longer works with this library.

However, the docs still say

The command line interface based on click introduced in Flask 0.11 is also supported. This extension provides a new version of the flask run command that is appropriate for starting the Socket.IO server. Example usage:

$ FLASK_APP=my_app.py flask run

[miguelgrinberg]

The flask run command is still available and functional. The difference is that it cannot be used to start a production server anymore, so it is now fully aligned with Flask on this respect. So yes, the docs are a bit misleading, but not exactly like you are describing, I think it should be noted clearly that flask run runs the development web server.

[willthames]

It's not just that, but that you don't get any websocket features at all with flask run (at least that was my understanding from the message printed out when I started my app). I'd be happy with the development server for my purposes, except for that.

[miguelgrinberg]

Yes, that is correct. The development server from Flask does not support WebSocket at this time. This is already mentioned in the docs elsewhere, but should also be noted where flask run is discussed, agreed.

[willthames]

Thanks @miguelgrinberg - I just found it a little confusing.

BTW I've reused your example for my docker-debug application, it's super helpful
https://github.com/willthames/docker-debug#websockets

Yours was one of the few examples I found with an open source license, I've reused the same license and tried to give you appropriate credit in the docs and source code