Create GitHub Actions workflow to generate PDF

[sualeh]

I love this article. You can consider adding a GitHub Actions workflow to generate the PDF automatically each time a content change is made.

[sualeh]

This will test your script with a CI/ CD build.

[ar]

Agreed this is worth having @sualeh, and recent history proves it: the last few fixes (#7, #8, the pandoc flag fallback in #10) were all breakage on platforms this script never sees between releases, exactly what a CI build would catch on day one.

The plan is slightly different from a plain workflow, because the dependency stack (TeXLive/XeLaTeX, pandoc, the pandoc template, m4, mermaid-filter with a headless Chromium) is heavy and slow to install on every run: we'll probably have to publish a memo builder container image with the full toolchain baked in, as a public image. The GitHub Actions workflow then becomes trivial—run the container, memo memomemo.md, upload the PDF as an artifact—and the same image doubles as a zero-install way for anyone to use memo locally (docker run -v $(pwd):/work jpos/memo memo mydoc.md).

Keeping this open to track the image + workflow pair.