[mediacapture-output] Option to remove consent for default audio device? (#89)

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

== Option to remove consent for default audio device? ==
In the [consent](https://www.w3.org/TR/audio-output/#privacy-consent) section:

> The default audio output device is always authorized.

That seems problematic unless there is a "null" output device. I often want all web pages to be unable to make sounds (I typically do that at the hardware level by inserting a blank jack into the headphone output, but that is suboptimal).

It looks like there should be an option for the user to **remove** consent from the default audio output device.

Please view or discuss this issue at https://github.com/w3c/mediacapture-output/issues/89 using your GitHub account