Repo contains excess files, remove excess files

[Hotrian]

Some people have had difficulties building this because they miss the "Made with Unity" part, and attempt to build this repo directly. This repo is intended to be run through Unity, so it does not need the .sln or .csproj files. It also does not need any of the Library/ files, except LibraryFormatVersion.txt and LastSceneManagerSetup.txt. I will remove these excess files when I have a chance.