Add release GitHub Action

[cbrnr]

Fixes #103. This needs to be tested, since I've basically just copied the yml from MNELAB. In particular, we need to make sure that we've added the correct access token to upload to PyPI.

[cbrnr]

I think I've set up the required trusted publisher info in pyxdf's PyPI settings, so maybe we're good to go?

Here's the how-to in case anyone wants to read up on it and check if this PR works correctly:

https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/

[cboulay]

I don't mind if you stumble through a few minor version bumps while setting up the release. Go ahead and merge and release and let's see!

If you don't want to do that then you can try

with:
    repository-url: https://test.pypi.org/legacy/

(After creating credentials on test.pypi.org for this package)

[cbrnr]

OK! The risk isn't even that big, because if the upload to PyPI works, everything worked! If there's an issue, I can always delete the tag and force-push (I've done that in some other projects 😄).