[Suggestion] Add tag_collection to items

[Darxo]

A tag_collection, or flags is a vanilla concept which allows an object to save a countless amount of additional data at will while staying savegame compatible.

If Items had this tag_collection then that allows cosmetics mods for armor/helmets, which are removable again because they use the flags.
E.g. https://www.nexusmods.com/battlebrothers/mods/107