In the context of [1], we're doing the first step and restructure our
documentation according to Diátaxis [2]. No content changes were made,
just restructuring everything according to the framework. All the
additional stuff which has been started in !630 like building separate
documentations via make files which then get interlinked via sphinx-
interlink have been left out for now.

[1] meta#8
[2] https://diataxis.fr/