Suggest: convert to MkDocs and markdown

[richelbilderbeek]

Currently, we use ReStructuredText and Sphinx. Compared to markdown, RST is a lesser known language and -from my perspective- this course is the only one that uses RST.

The low use of RST has some negative consequences:

• We need to set up new CI tools
• We cannot copy-paste our work from most other sites (assuming -like for me-) most other websites) use markdown too

Using markdown would fix this.

Richel volunteers to convert!