Documentation setup

Introduces a setup for creating documentation with sphinx and sphinx-rtd-theme via CI runner

Closes #2315 (closed), #2308 (closed)

Example HTML-output can be seen here updated 2024-05-11 00:15h UTC

ToDo:

• theme is currently the rtd default theme, could be modified for pmos (could also be done later) as discussed the theming will not be part of this MR
• CI runner will need modification for publishing the html docs of the master branch --> will end up in /public
• docstrings of about 500 elements in pmb would need to be written --> #2351
• usage section is very very basic at the moment --> improved by using sphinxcontrib.autoprogram
• links to wiki could be added e.g. troubleshooting