Support For Granular Locking Mechanisms.

[flaxinger]

Details

First of all, we really thank you for this project. It's really one of my favorite GHA related projects.

The Problem

We recently realized that sticky locks lock on a user level, not on a PR level. This recently caused a problem for us because one of our developers forgot to merge and deployed another PR, effectively rolling back the changes of his previous PR.

The Suggestion

We would like it if locks could also work on a PR or Branch basis.

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I would be glad to contribute if that's ok, but I wanted to check if my assumption and suggestion was valid first.