[Request] Option to randomly select game music as background music

[cnapolit]

Thought this would be an interesting/quirky feature to have. Instead of playing the default background music, a random song from any of the available games is selected and played. Would have to collect all file paths first to avoid any selection bias. That might make it a little heavy (especially for larger libraries), but since it would only occur every 2-8 minutes, I doubt users would notice.