Alternate proposal for processing and generating MediaStreamTrack

Hi all,

Following on last meeting and discussions on GitHub, I wrote down a proposal for being able to read frames from a MediaStreamTrack and create a MediaStreamTrack from a JS source.
This is available at https://github.com/youennf/mediacapture-extensions/blob/main/video-raw-transform.md <https://github.com/youennf/mediacapture-extensions/blob/main/video-raw-transform.md>.
I will also have the pleasure to present it during this week WebRTC WG interim meeting (slides available in the meeting slide deck).

Feedback is very welcome.

Thanks,
	Y