[mediacapture-fromelement] Clarify if CanvasCaptureMediaStreamTrack mute, unmute, and ended events are expected to be fired (#82)

guest271314 has just created a new issue for https://github.com/w3c/mediacapture-fromelement:

== Clarify if CanvasCaptureMediaStreamTrack mute, unmute, and ended events are expected to be fired ==
`CanvasCaptureMediaStreamTrack` has `mute`, `unmute`, `ended` events.

`mute` and `unmute` events of `CanvasCaptureMediaStreamTrack` are not fired under any cases or circumstances at Firefox or Nightly. 

Chromium fires `mute` and `unmute` events for `CanvasCaptureMediaStreamTrack`.

@Pehrsons clarified that Firefox is currently specification compliant by pointing out that 

> A [mute](https://w3c.github.io/mediacapture-main/#event-mediastreamtrack-mute) event is raised on the MediaStreamTrack when content availability changes.

is specified 

> for HTMLMediaElement capture, not HTMLCanvasElement capture

https://bugzilla.mozilla.org/show_bug.cgi?id=1598237#c28.

Kindly clarify if `mute`, `unmute` and `ended` events, are applicable to `CanvasCaptureMediaStreamTrack` or not - in the specification.

Please view or discuss this issue at https://github.com/w3c/mediacapture-fromelement/issues/82 using your GitHub account