Attempt using GitHub Actions to auto-build PDFs

[ripleymj]

I saw a mention of this repo earlier and wanted to see if I could apply a trick we use for the UUG presentations repository. After a few small changes, this uses GitHub Actions to run your build.py, assemble a zip of the resulting PDFs, and publish them as a release artifact on GitHub. The zip is not committed, so it won't explode the size of your repository. Also, because it deletes the previous release and publishes a new one on each push to master, you end up with a fairly stable URL to link to: https://github.com/ChrisMayfield/cspogil/releases/download/cspogil-latest/PDF.zip (after the first run completes).

If you want to see what a run looks like, my misfires are all archived here: https://github.com/ripleymj/cspogil/actions

And if this isn't a direction you want to take the project, no hard feelings if you just close the PR.

[ChrisMayfield]

Awesome, thank you for this! Yes I would like to go in this direction. I've been wondering the best way to include PDFs in the repo, and having them as a release artifact makes a lot of sense.

I'll get to this PR in the near future. First I'd like to make some minor changes (e.g., build student versions by default) and also merge in some improvements we've made in the Makefile for the Python collection (currently stuck in a private repo).