[llvm] [Github] Add labels on pull requests based on paths. (PR #65308)

[Tobias Hieta via llvm-commits]

tru wrote:

> This has not been tested, not sure how testing that sort of change can be done.

Push to your fork and open a PR towards your fork instead of main.

This looks fine to me. It's a shame that we can't use the same mapping as CODEOWNERS since this means we will have to dupe the "rules" in both places. But I still think it is worth doing.

https://github.com/llvm/llvm-project/pull/65308