add workflow for trusted publishing

[HLinde]

Hi and thanks for your nice project! :)
I use chemformula in on of my projects and just went through learning to package it via github to pypi. As you mentioned in #15 that such PRs would be welcome, I put something together in case you are still interested.
I used uv (https://docs.astral.sh/uv/) as a project manager (just this basically: uv run pytest) and it is used in the publish workflow.

To finish this you would have to do those two steps:

• To use that so-called "trusted publishing" you have to link your Github in pypi, see https://docs.pypi.org/trusted-publishers/adding-a-publisher/
• you have to create the "pypi" environment for the github-repo in Settings -> Environments. In my project I added also Deployment protection rules: Review required and 5 min wait timer.
• update the version in pyproject.toml before new releases

Once that is set up, the workflow is triggered by creating a proper "release" on Github.

In case you are interested to publish also via conda-forge, setting up a recipe for them is not so complicated either (https://github.com/conda-forge/staged-recipes?tab=readme-ov-file#generating-recipes-with-grayskull). However you need to have all dependencies also in conda-forge apparently. So I would be quite interested to have chemformula also in conda-forge ;)

[HLinde]

I added the conda-forge recipes here: conda-forge/staged-recipes#30634
Let me know if you want to be listed as a conda recipe maintainer!

[molshape]

Hi @HLinde, thanks a lot for your feedback - I really appreciate your contribution! 👍 I'll try to review the pull request next weekend, but I already like your suggestions and will add GitHub as a trusted publisher on PyPI.
Thanks also for linking the relevant documentation - that definitely saves me some time.

I also like that you've created a Conda recipe. No need to list me as a maintainer, though.

[molshape]

Thanks for you pull request, @HLinde! I've successfully merged your pull request into main.

[HLinde]

I was happy to help and thanks for your continued work! :)

[HLinde]

@molshape Just wanted to let you know: casregnum and chemformula were included to conda-forge today! 🎉

[molshape]

@HLinde Hey, cool, thanks for following up and letting me know! 🎉 And thanks a lot for your support and pushing this to conda-forge. 🚀