What does this datapack do?
All it does, essentially, is make it so that when you put 9 charcoal into a crafting table, you get 1 coal block out of it. And then I suppose you could craft 9 coal from that. Good if you don't want too many unique items and instead you just want stackable items, or you just don't like charcoal. Understandable. That's all that this datapack does and all that it will ever do.
