[llvm] [GitHub] Add Greeting comment to new PRs with useful information (PR #72249)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Example PR: https://github.com/DavidSpickett/llvm-project/pull/23

The mechanics are right I think, probably needs tuning so the right level of notifications are sent. I can look into figuring out if the author is new to the project, or the lower-tech version of that is a team you can join to opt out of these messages.

It could be done as part of the subscriber workflow, which already has a way to know if it has left a comment previously. That's one way to know what order all this will be done if that's required.

https://github.com/llvm/llvm-project/pull/72249