Adding a merge queue

[javiercasares]

This may be interesting to apply to the repo.
https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-a-merge-queue#managing-a-merge-queue

[LinuxJedi]

Oh interesting, it is the speculative merging feature we wrote Zuul for like a decade ago. Not sure if we have the traffic for that yet. But definitely something to look into.