Add macOS setup docs and build/run helper scripts

[adeeb10abbas]

Personal setup for building and running reVC on Apple Silicon (M5):

• docs/MACOS_SETUP.md: full instructions (build, game data, audio, windowed mode, controls)
• scripts/build_macos.sh: one-shot build using Apple's clang (Homebrew LLVM breaks librw) and generating the gitignored GitSHA1.cpp
• scripts/run.sh: launch reVC from the game data folder

As long as it's not linux/cross-platform skeleton/compatibility layer, all of the code on the repo that's not behind a preprocessor condition(like FIX_BUGS) are completely reversed code from original binaries.

We don't accept custom codes, as long as it's not wrapped via preprocessor conditions, or it's linux/cross-platform skeleton/compatibility layer.

We accept only these kinds of PRs;

• A new feature that exists in at least one of the GTAs (if it wasn't in III/VC then it doesn't have to be decompilation)
• Game, UI or UX bug fixes (if it's a fix to R* code, it should be behind FIX_BUGS)
• Platform-specific and/or unused code that's not been reversed yet
• Makes reversed code more understandable/accurate, as in "which code would produce this assembly".
• A new cross-platform skeleton/compatibility layer, or improvements to them
• Translation fixes, for languages R* supported/outsourced
• Code that increase maintainability