[mediacapture-output] Setting the output for a whole context (#87)

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

== Setting the output for a whole context ==
Currently, we are only able to control individual HTMLMediaElement audio output with setSinkId.
We probably need to add something to WebAudio as well.

In most cases, it seems that pages will want to output all their audio to a single device.
Adding such an API to do so would be convenient and would complement setSinkId which would be used to override this default value.

Something at navigator.mediaDevices level might make sense.

Please view or discuss this issue at https://github.com/w3c/mediacapture-output/issues/87 using your GitHub account