Abilities: Origins in a Datapack

SHADOW ORIGIN REMOVED! Due to incompatibilities with 1.21. Probably not going to come back, but the code is still there in case of the future revival

• Updated to 1.21 (damn so many changes to command syntax and datapack syntax)
• Elytrian elytra code overhauled (not much gameplay changes)
• Avian code overhauled (no gameplay changes as of yet)

To be added:

• New abilities to take advantage of new 1.21 features
• Overhauling more old code to take advantage of new 1.21 features, like I did for 1.19.4