1.20.1 fixes and backports

[unilock]

This PR makes a number of changes:

• Some things have been backported from the 1.20.2 branch:
  • A GitHub Actions workflow has been added
  • Contributors have been added to fabric.mod.json
  • Gradle, Loom, and dependencies have been updated
  • Codec<T>s are now used for LootConditions (wrapped in a universal JsonSerializer<T> at registration)
• All images in the repository have been optimized, making the mod JAR a bit smaller
• Fabric's Data Attachment API is now used for fireproof ItemEntity and FishingBobberEntity instances, which should fix [1.19.2] Items disappear due to invalid data #101
• The AccessWidener has been removed, as miscellaneous code changes have made it no longer necessary
• The mod's biome tags now (optionally) include Fabric's convention tags, which should improve compatibility with other mods that add biomes (as long as they add them to the appropriate tags)
• The End Crate now has a loot table as a block, fixing Placed End Crate has no loot table [1.20.1] #110
• Code has generally been cleaned up and updated across the board