Add export to external repo service

[dnil]

It would be useful to have Abacus available from build services, such as PyPi and bioconda.
This should be automated ideally; I can help with that if you like, but it would be nicer if you register them so the maintenance and authorship is super clear.

[dnil]

Hi @ThomasAls and @jakobjn! What about this one? The pipeline devs were more enthusiastic about PyPi than bioconda, but either is fine. It will take admin access to the repo at least for the final steps of setting up a "trusted publisher" with PyPi. We will also have to give it a slightly more qualified name, as "abacus" alone is taken as a python package.
I think I will just try to make a PR to bioconda for now: this does not really require stating anything about ownership etc - I would just point it to pull from this repo, and we can see what gives.

[dnil]

Speaking of that, it would be A Good Thing to have a release, both to start slowly incrementing version with changes, and to have something distinct to point to from bioconda. It's probably fine if it's the 0.0.0 release for now!

If you are not used to this, the GitHub docs surely has it (https://docs.github.com/en/repositories/releasing-projects-on-github/about-releases), but there is a button just next to the branches that says "Tags", and from it a maintainer can choose "Releases" and then "Draft new release". Set the release pointing to master and the new tag to contain the package version from the setup.py - e.g. commonly like "v0.0.0".

[dnil]

Like so: bioconda/bioconda-recipes#59406. Here we'll need to provide a release version, matched to the release tag.