Feat: extra source files local install

[RedBrumbler]

things like additional source files (like src/inline-hook for bs hook) do not properly work with local installs of packages, and are unable to be found:

Error:
   0: Missing extra src/inline-hook for dependency beatsaber-hook:3.15.0

I assume this is because local installs purely allow the shared & built .so files to be symlinked, and none of the additional files