Allow for Twitch.tv live transcription

[keyehzy]

trafficstars

As for issue #209, this works.

We rely on streamlink library to give us a stream, then we proceed similarly to the radio livestream example.

I also didn't find a straightforward way to handle twitch stream but we can work around using this external tool. Note that the user need to install streamlink for this to work. See link for how to install it. That being said, this application supports many plugins for other streaming services so it would extend whisper.cpp reach quite a lot.