Add required metadata that states the mod is made with MCreator

When making modpacks or deciding which mods to use, some people prefer not to have MCreator mods because they slow down game performance, but it's impossible to tell if a mod is made with MCreator unless you look in the code. The MCreator tag on CurseForge is helpful, but it is optional. It would be great if the mods.toml or fabric.mod.json had a field in all MCreator mods that made it clear so mod hosting sites like Modrinth and Curseforge could filter for it and apply the category automatically.