Approve all workflow runs for a specific contributor PR

[jprochazk]

What

This PR adds the ability to approve workflow runs on forks on any current and subsequent changes automatically. This is a step above the "don't approve any workflow runs on forks automatically" that we have set up right now.

The approval is triggered by commenting on a PR issue (issue_comment), or the usual PR activity (pull_request_target). It then looks through all comments on the PR, searching for the substring @rerun-bot approve. If it finds at least one, then it checks if the user that sent that comment is any of:

• A repository owner
• A member of the repository's organization
• A repository collaborator

If that is the case, then it approves all workflow runs on that pull request.

PRs cannot modify this workflow or the script it uses to change how it works. The changes must first be merged into the default branch before having any effect, so this is safe for contributor PRs.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested demo.rerun.io (if applicable)
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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