port to 1.20.6

[ix0rai]

• port to 1.20.6
• all new config!
  • new screen, that's more beautiful!
  • provide more information, such as how many datapacks are loaded to add extra modes
  • use quilt config as the backend
  • make rarity per-entity
  • your config from 1.2 will NOT BE MIGRATED! if you'd like to keep your values, please copy the file elsewhere and use the GUI to change the settings back in the new version
• properly remove vanilla mode
• updates to server sync
  • sync entity toggles and rarities
  • server sync is no longer optional
• improve particles for slimes
  • slimes now use slime block particles everywhere - thanks @orifu for this change!
  • fix an overly huge amount of particles being spawned with each jump
• disallow using dyes on mobs when they are disabled in the config

TODO:

• Config Options for Separate Mob Colors #16 - delayed
• add buttons to sync values between all entities - no
• add coloured yes/no text to config to improve clarity
• fix slime particles ( @orifu this isn't happening unless you make me textures <3333)