Build zip files for bare metal exercises #529
Description
The bare metal exercises currently require copying and pasting a lot of files to get started, which is annoying and error-prone. Some students check out the repository instead, but then they get model solutions rather than just the starting template. It would be better to have a script and GitHub action which automatically builds the template, using the same marker comments as the mdbook includes use, and then makes it available to download somewhere (maybe as a release or artifact?) linked from the mdbook.