Adding a workflow to generate source code documentation using Doxygen (Sphinx was the other option but that mixes a bunch of configuration files with the source code, which is messy). As far as I am able to test this set up it successfully generates the documentation in HTML format. However, at present the contents are limited by the fact that the code does not contain any doc-strings to generate documentation from.

In the current set up the documentation is automatically pushed to a GitHub Pages branch on the repo (gh-pages). On the first attempt there are likely going to be some issues as a few additional configuration steps on the gh-pages branch are required (https://github.com/peaceiris/actions-gh-pages#%EF%B8%8F-first-deployment-with-github_token).