Live subtitles for streams

[iccanobif]

This is a sloppy AI generated live subtitles feature.

Problems:

• It seems to be working only on chromium browsers. Would be nice to find a way to make it work on other browsers as well.
• Only works for english (support for other languages can be added, apparently)
• enabling/disabling subtitles is a preference, but it might be better to have it as a flag directly in the stream panel?

Possible solutions:

• Have the streamer generate the subs on his side and send them to everyone else through the websockets. Rationale: I get the impression that all browsers support speech2text given that the audio source is a local microphone, rather than a generic MediaStream.
• Or maybe subtitles should be generated server side? Probably difficult to do before the refactoring that removes janus.