Adjust/refactor/improve/split README for great justice!! (and better devex)

[hmpf]

Freshly home from the first (best?) conference of the year, FOSDEM 2025, we have been inspired by the following talk: Beyond the README: Crafting a Better Developer Experience for Open Source Projects.

We should:

• [x] Add topic tags (for discovery) to the github repo
• [x] #1169
• [x] #1168
• [ ] #1167
• [ ] #1166

Non-docs related improvements mentioned in the talk belongs in a separate issue.