[llvm] Document the requirement that commits have a public email address (PR #109318)

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

> Are we gonna "upgrade" the bot message from a soft message to more of a requirement? Considering the current dynamic since I raised this, I just ignore the bot and merge PRs (like most people it seems) at the moment.

To be honest, I don't know. I figured we'd get the policy down on paper first, then we can post another RFC to see if we want to strengthen the enforcement of the policy further. Personally, I'm comfortable with the soft action so long as the person landing changes on behalf of someone is willing to take responsibility for reverts if necessary. But the RFC thread was mixed on how firm we should be with enforcement, so I didn't want to change behavior with this PR.

https://github.com/llvm/llvm-project/pull/109318