[llvm] [llvm][docs] Document how to ask for things other than commit access (PR #146340)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Maybe we do document this but I looked in the triage guide and it wasn't there, I don't recall it anywhere else. Tell me if so, we can move/link one place to the other.

https://github.com/llvm/llvm-project/pull/146340