Neutral GitHub checks for stacks without changes

As per our user's feedback, we introduced a small but rather visible change to how runs with no changes are reported to GitHub. Previously we reported no-op runs as successful which made it harder to pick out the really interesting ones. Today we started reporting them as neutral, which GitHub still considers to be passing for the purpose of branch protection.

We hope that our GitHub users find this change useful. If you have any feedback, please let us know. If you're interested by the intricacies of the GitHub API, you can learn more about the Checks API here.