reStructuredText files

An alternative to markdown

https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html

Conversion

Sphinx can be used to convert .rst files to HTML, PDF, LATEX etc

https://www.sphinx-doc.org/en/master/usage/quickstart.html#setting-up-the-documentation-sources

Projects do this all the time

Compared to markdown

Offers more features than markdown, more systematic
Markdown is simple and easy