Merge queue for the build system

[fbnrst]

What change(s) are you proposing?

In our fork sequencing-docker-stacks, we make use of the Mergify merge queue. Given the long build times of the images, I find this quite helpful.

I see the main advantage, if you have 2 or more PRs at the same time. If one of them is merged, then the other PR needs to be rebased, and tests have to run again. The merge queue chains both PRs in a draft PR, and then runs the test on the combination of both of them. I found these situations very time consuming, not sure whether this is an issue for you as well.

The main thing that is needed to set this up is a config like this one: https://github.com/huchlab/sequencing-docker-stacks/blob/main/.mergify.yml

I'm happy to discuss this further, if you are interested.

How does this affect the user?

no effect on user, but potentially can speed up merging PRs

[mathbunnyru]

If you have time to make it work for the main repo, I will be happy to review and try it out!