Alpha Update for 1.21-pre1

Changes:

Remove PortalHorse as they added it to vanilla
Minor changes to Identifiers of mounted modifiers
Major rewrite of all rendering code

How to use:

ModMenu/ClothConfig don't exist for 1.21 yet. Download their latest versions and the mod will work.

Edit config/HorseBuff.toml if you need to edit config.

Known issues:

Opening ModMenu crashes the game. Unsure if this is at fault of ModMenu/ClothConfig

Partally translucent horses (from looking down with Horse Fade enabled) often hide stuff that is rendered behind them, even with graphics set to Fabulous! Player looking down while on horseback with a llama in front of them. The horse is partally transparent and you can see stuff through it. The llama isn't visible through the horse. Parts of the horse's shadow aren't visible through the horse