Add ChikuTaku as background music

[Joss3Dev]

I think it would feel good to listen to Ame's original while waiting for her

[GrygrFlzr]

Worth noting autoplay audio is blocked by default on basically every major browser, so while possible this would have to be behind an explicit Play BGM button (or any other similar button that involves user action). Additionally, there are potential copyright concerns for redistributing the song.

[Joss3Dev]

you're right about the copyright issue, pain peko