Visible feedback for keyboard shortcuts

### Your use case

In calls it seems like users are accidentally muting/unmuting their inputs and not realising when they're doing it. We should display visible feedback for keyboard shortcut input. Open thoughts:

- We should benchmark how other video calling apps handle this to see if there's any affordances we should meet, and get confidence in the overall info architecture
- We could consider a shortly lived toast or snackbar
- We could also take inspiration from YouTube - they momentarily display an icon in the middle of the screen confirming your keyboard action - visible enough, and not too annoying when used multiple times

### Have you considered any alternatives?

_No response_

### Additional context

_No response_