This update implements the elusive 1.15 donkey dupe!

Player 1 opens a donkey's (or other horse-like) inventory, Player 2 rides the donkey and then disconnects.
Player 1 is left with a duped inventory that they can remove the items from.

This dupe works like vanilla when more than one player tries to dupe using the same donkey (they all share the inventory) and it even works with donkeys inside boats!