How to go about taking down a repository that houses a mod that is used to steal copyrighted material

I recently came across a website that takes and republishes content from a game called VRChat the content that they host is copyrighted and paid for material that they do not own and the mod thay use to take the content from the game is hosted here on GitHub

Not only is this mod required to take content from the game it’s also what they require people to use to be able to use the content that is stolen