Now Playing.md

Reinstate/port Pixel OS's Now Playing service

1. Install, pair, and start Shizuku (https://github.com/e-t-l/GrapheneUX/blob/main/Shizuku%20system%20privileges.md)
2. Install Ambient Music Mod (https://github.com/KieronQuinn/AmbientMusicMod)
3. Follow in-app instructions