Implement a PAKFileSystem to load archived mods

[EliteMasterEric]

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Let people install mods as a large compressed binary file which is decompressed at runtime.

One major downside to this method is that contents must be held in memory at all times

An implementation of PAK archives: https://gist.github.com/larsiusprime/5fd2c7ebbb787c3890b0

Also see about embedding the header into the PAK file.