Add PR number to output when triggered by push

[teleological]

It might be desirable to output the pull number when handling other triggers, but I wasn't sure what would be useful in the case of check_run, when multiple PRs might be merged, so I kept my change narrow.

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[ghost]

DeepCode Report (#d6a2c7)

DeepCode analyzed this pull request. There are no new issues.

[Logerfo]

Thanks for the PR. Did you find yourself any useful workflow using the new output? About the multiple PRs, what do you think about returning comma separated ids? It's a shame that return an array is not supported...