Make item animations tied to resource packs instead of being hard coded

For Java. Making it possible to have player animations that play when holding or right clicking an item would make it possible to create more advanced datapacks, enhancing creativity, and the ability to add gestures or emotes to multiplayer servers using a resource pack. You could use this in conjunction with the new custom_model_data, and change a spyglass so that when you right click, it looks like you're casting a spell! You could have a guitar item that looks like you're holding it across your chest, and strumming it when you hold right click. You could have a bow that looks like a chair, and you hold it over your head and then throw it when the arrow fires! This would be an awesome technical change, and resource packs would be able to have just a little more of their own unique flair.