[llvm] Document use of `skip-precommit-approval` label for non-review pull requests (PR #81053)

[David Blaikie via llvm-commits]

dwblaikie wrote:

> As far as I'm aware, there hasn't been any work done on implementing this on the subscription side? We should probably wire the label into the subscription job so that we don't end up sending extra notifications (which was part of the original RFC from what I understand), unless I'm missing something and that has already been done.

Honestly, I'd like to have that - though I know next to nothing about how the email subscription job works and at least a label would be better for me than the current state of affairs. So I'd consider this patch to be incremental improvement and further work such as subscription improvements would be quite welcome - I'd even take suggestions/pointers as to where the emails are implemented & I'd have a go at making that improvement.

Perhaps @tstellar can point me in the right direction for that?

https://github.com/llvm/llvm-project/pull/81053