Add Mergify config

[hugovk]

For python-pillow/Pillow#4900.

This has these rules:

• approved by more than one person
• has automerge label
• Travis CI has passed

Note that you cannot approve your own PR. And the rules for GHA is a little different than Travis, so let's with the simpler repo.

Docs for reference: https://doc.mergify.io/actions.html#actions

To test

When the CI is still running (or if it finished already, restart a job or the whole thing), approve and add the automerge label.

It should merge once the CI finishes.

[hugovk]

Actually, I removed this push rule, because the push happened on my fork, and only the PR one is visible here:

      - status-success=continuous-integration/travis-ci/push

[hugovk]

@radarhere Please could you test this? Thank you!

[radarhere]

Did you mean like that, by approving and labelling? I guess it doesn't apply until it is actually merged.

[radarhere]

If you want a PR to test it on, I can offer you #85

[hugovk]

Did you mean like that, by approving and labelling? I guess it doesn't apply until it is actually merged.

Yes. Could be, will merge and test with #85. Thanks!