Add support for merge_queue about app

[gr2m]

I'd be happy to accept a pull request, I didn't run into the problem mysel and haven't worked with merge queue yet

[webknjaz]

+1. This deadlocks merges when used with branch protection. This is what this looks like:

As for the events, GitHub generates two — merge_group for when a PR is added to the queue, but it also merges the PRs in the queue together into a temporary branch, which is an implementation detail but it also means there's a push event.

So basically, it'd be necessary to report a new Checks API status for one of these events. For the push event, it's possible to filter out the related ones by the read-only tmp branch pattern.