Recursive & downloadable outputs example

[stephlocke]

This goes through each folder and outputs any md files to docx. Github Actions then makes the output directory a zipped download. Developed during problem solving, posted it on https://stackoverflow.com/a/65091856/2257093

This shows how to go off the "happy path" of a simple pandoc call inside github actions and covers common requirements (accessing files and batch transformations).

[alerque]

I definitely like this way of working with Actions and employ the model myself quite a bit. That being said, I think this needs a little bit of fleshing out before we can merge it. In particular the README should be documented similarly to the way the other actions are explained. Also somehow we would need to adapt this repository so it would run sensibly on it. I don't want to clutter things up too much, but only having one Markdown file and no directories to work with does make it kind of hard to show off this particular usage.