Context: https://linear.app/comm/issue/ENG-2386/app-is-pausing-background-media-playback-after-videoplaybackmodal-has

Basically copy/paste this line: https://github.com/react-native-video/react-native-video/blob/master/API.md#audio-mixing

This diff should allow background media playback to continue over any foreground media playback.

This doesn't completely resolve the issue because we DO want to prioritize foreground media playback and pause background media if a video is actively being viewed, the problem is that the app is blocking background media playback even with no video is actively being played.

1. Open video message in Comm and begin media playback
2. Navigate back to the ThreadList
3. Open Spotify/Apple Music/etc and begin playing audio that'll continue playing in the background
4. Foreground Comm and make sure that background media playback doesn't get stopped