Study Screen: Add 'Pause Audio' action

> [!CAUTION]
> This issue exists for documentation and is not yet workable. Asking to work on it or have it assigned to you is like asking us to stop considering your contributions. Act accordingly. Thank you.

https://github.com/ankitects/anki/blob/93c44335f672bc02e834c369fd65a9c39a4c823b/qt/aqt/reviewer.py#L1036

https://github.com/ankitects/anki/blob/93c44335f672bc02e834c369fd65a9c39a4c823b/qt/aqt/reviewer.py#L645-L647

See:
- https://github.com/ankidroid/Anki-Android/pull/19598
- [Add audio actions](https://forums.ankiweb.net/t/add-audio-actions/62667) (Anki Forums)
- https://github.com/ankidroid/Anki-Android/issues/6774

The current implementation needs more explanation, and how/whether AnkiDroid implements this functionality is also subject to discussion.

We do not use `mpv`, and have multiple methods of playing audio [webview (audio/video), system audio, TTS, audio recordings]