[llvm] [DirectX] Documenting Root Signature Binary representation (PR #131011)

[Justin Bogner via llvm-commits]

https://github.com/bogner commented:

Various editorial notes. From a high level I think it would be helpful to describe what's in the various parts of the format before showing example C structs to describe those parts, and I think we need to be more explicit about what's laid out where in the format rather than going into a lot of detail about what the fields are used for.

https://github.com/llvm/llvm-project/pull/131011