Huge behind the scenes update:

• Converted to multi-loader setup, so I can develop for forge and fabric at the same time.
• Added more compatibility with better nether, better end, and gardens of the dead
• Fixed flickering issue when changing the selected index. Especially noticeable on a server.
• Fixed flickering issue when using an item from a sack.
• Pick block now works on sacks, updating the selected index if no other item is in your inventory that it can fetch.
• Fixed various issues with inserting items into sacks/quivers/bundles when the item is the result of a crafting recipe.
• Fixed bug where the selected index would start at the wrong spot when changing it within a bundle.
• Added Container Item behavior API, which lets developers easily add more container items without having to create more mixins.
• Renamed sack_type_default and sack_weight_default to sack_type_rule and sack_weight_rule.
• Added sack_type/none item tag, which prevents items from being inserted into sacks.