Change source directory to a less generic one.

Why: https://wofsauge.github.io/IsaacDocs/rep/tutorials/Using-Additional-Lua-Files.html?h=command#the-namespacing-problem-with-require

Fixrelease not actually including latest patch.

Release changes reminder:
Fade out music when playinx SFX.
On Afterbirth, pause it instead (can't fade in/out without Repentance).

Fade out the music when playing SFX

Without Repentance, it will be paused it instead. That's a little bit less smooth, but the functions to fade in and out are a Repentance exclusive.

Remove unnecessary files

Quick description fixup (was still using the draft)

v1.0 release