Create GitHub Actions for PR reviews

[corrideat]

Problem

pull-review-crush.yml and pull-review.yml are pretty long and need to be kept in sync across multiple repositories.

Solution

For pull-review-crush.yml and pull-review.yml, consider creating an Action (if that's the proper name) in a repository, so that it can be used in workflows by referencing it with uses:. This is the same way that, e.g., actions/checkout works. That way, we can use them by creating a small workflow file with uses: okTurtles/review-crush@latest or something like that.