Documentation in two places and inconsistent

Recently, we had a short discussion where to put new documentation. There is the documentation on the website (https://docs.openml.org/developers/) and documentation in the Wiki (https://github.com/openml/OpenML/wiki)

Keeping this in two places is bound to cause problems in the future, or already does create problems (both forms of documentation are only partly intersecting). I propose that we do either of the following:

• Move documentation from the wiki to the frontpage
• Move documentation from the frontpage to the wiki
• Keep "OpenML usability" documentation on the frontpage, but put developer related issues in the wiki (how to extend openml with new packages, basically all stuff we discuss on the workshops)

Start by reviewing the developer documentation at https://docs.openml.org/developers/ and the OpenML Wiki, then inspect the existing discussion about where new documentation belongs. A contribution would need an agreed documentation structure and a completed migration or clearly documented division of content, but this issue does not identify files, tests, or a decided direction.