Allow "Trims" on any items in datapacks

The armor trims are great as they are, and the ability to make custom ones for datapacks is one of my favorite parts, but it feels like there's a lot of unused potential with the implementation of it in datapacks. Currently the game is hard-coded to only allow trims to be applied to armors- even if you create a recipe which accepts other items- and whether it already is a plan or not, I believe the system could see a lot of benefit from being generalized. So, rather than making the recipes add "trims" on to armors, simply refer to them as "additions", and allow the addition name ("trim" for armors, or "gilt" for swords, etc.) to be defined in the datapack itself. This will allow for customizable functionality such as visually marking tools with different enchantments, or for the hard-core datapack creators, making enchantments and tool types of their own!