Revamp / cleanup of OpenRefine's Wikibase documentation

OpenRefine started off with Wikidata support, and is now also increasingly supporting arbitrary Wikibases and now also Wikimedia Commons (yay!)

This is great, but our Wikibase documentation is still structured as a remnant of the old Wikidata-centric situation. Wikibase documentation has been added over time in various places, and in OpenRefine/OpenRefine#5023 I shoehorned in some documentation focused on Wikimedia Commons. But as a whole, IMO the documentation has become a bit inconsistent and potentially confusing for end users. I think it would be great to dedicate some time to a future-proof re-edit of that entire section.

Proposed solution

Fresh reorganization of the Wikibase support section. Some of my thoughts here:

• I think it's good to often explicitly mention both Wikibase, Wikidata, and Wikimedia Commons. Wikidatans and Wikimedia Commons users may not be familiar with the term 'Wikibase' at all.
• I have a hunch that we are mostly serving three distinct groups of users with this documentation: Wikibase users, Wikidatans, Wikimedia Commons editors. This may need a bit more research and testing, but I think it does make sense to provide various entry points if these are indeed large distinct groups (even if the back-end features, and the Wikibase extension as a whole, are considered as a holistic architecture from the technical side).

Additional context

Maybe we can fit this into the upcoming Wikibase-focused work (roughly July-December 2022) which will be funded by NFDI.