[llvm] [Docs] Instructions for new contributors to find reviewers (PR #71936)

[Kristof Beyls via llvm-commits]

https://github.com/kbeyls approved this pull request.

LGTM, thank you!

I guess you may want me to merge this PR for you as you may not yet have merge rights?

https://github.com/llvm/llvm-project/pull/71936