Fixes: https://github.com/jitsi/jitsi-meet/issues/4049

* ref(feedback): emit api feedback submitted on completion

Compared to firing the event on submission because
the submission ajax will not be completed at that
time..

* squash: update package.json

- Use actions to notify the rest of the app that
  a mic or camera error has occurred
- Use middleware to respond to those notifications
  of errors by showing in-app notifications and
  notifying the external api

* feat(screenshare): emit source type when starting screenshare

* squash: update doc

We seemed to be using the names "film strip" and "filmstrip" (and,
consequently, their source code-conscious forms such as film-strip,
FilmStrip, etc.) In order to comply with our coding style which requires
a consistent one name for a given abstraction, choose one name and
rename the uses of the other name.

Wikipedia has a definition of a "filmstrip", I couldn't find a "film
strip". I guess our abstraction can be seen as what's described there.
When I google "film strip", I get results about "filmstrip" at the top.
That's why I chose "filmstrip".

Certain uses of "film strip" such as interfaceConfig.filmStripOnly and
in the external API I left untouched in an attempt to preserve
compatibility.

I wasn't sure whether CSS was tangled in compatibility so I made a
choice and renamed there was well.

- use proper punctuation
- fix markdown syntax
- always use syntax highlighting
- document missing commands
- miscellaneous grammar fixes

Fix videoConferenceJoined and videoConferenceLeft event names