Too Long; Didn't Read
Mergify is a free automation tool that works with any CI and integrates natively with GitHub. It helps prioritize, queue, and automatically merge your pull requests. It can also rebase and update your branches while commenting, labeling, assigning, and closing pull requests. It can do all the just mentioned. But, of course, you can do some of these things directly; well, some features are covered by Github, but you either need to activate them manually or are not.