added pack overlay so that only pre-1.20.3 versions get the old bat texture, allowing for a wider range of supported versions
note: lightly modded 1.20.2 had an issue detecting the pack when i tested it out, but a 100% vanilla instance of the same version had no issue, so it's possible a certain mod breaks resource pack overlays or something
Removed bat texture, now that bats have pixel-consistent textures in vanilla.
