This is very similar to Streamer Outfit Pack on the steam workshop. There is a github link on the mod page that brings you to the repository containing all the code. You can use that as a reference. As for how to actually do the mod, you will need some knowledge of C# and Unity.

Also, join the Unofficial PlateUp Modding Discord. https://discord.gg/uPbuYVjJQq There's a lot helpful information, and people, to ask when you have doubts there.