Adds a shuffle mode for local music files to the in-game radio.
Toggleable with F9. Automatically scans and loads the entire music library on first activation.
Provides compatibility with the "Radio Enhancements" mod.
Interferes with `SoundPlayer.startChannel` to prevent the song from restarting when switching vehicles – even when switching from "Radio off" to "Radio on".
The shuffle position is retained when switching vehicles.
