Completely refactored the entire resource pack!

Changelog:

• Added mod support for Regions Unexplored and The Twilight Forest!
  Creating the animated textures for The Twilight Forest was a pain...

• Updated the Aether Berry Bush model.
  The Berry Bush now has better Ambient Occlusion.

• Updated the pack.mcmeta to support 1.21.8.
  The resource pack works perfectly fine on 1.21.9-1.21.10, but due to how the new pack formatting works, I can only define "support" for either 1.20.2-1.21.8, or 1.21.9-1.21.10. Once 1.22 comes out, I'll be switching to the new pack formatting.
  

• Fixed the block textures rotating when the canopy position rotated!
  This issue was bugging me since the beginning, and I finally reworked the blockstate files (which was causing the issue)! I'm now using multipart models instead of replacing the entire model for rotations; so now the 'canopy' part of leaves can rotate independently from the block. These changes also allow me to share a majority of the files between the two variants, which makes updating things a lot easier.
  

• Updated the credits file.
• Updated the license file (the license itself didn't change).
• Fixed culling issues on opaque blocks.
• Fixed some canopy types having a lower spawn rate than intended.
• Fixed the Nether Wart canopy having it's texture offset by a pixel.
• Probably more that I forgot!