Why is the documentation in another repository?

I think that documentation should be in this repo, in a `docs` folder.
This could help in that when issuing PRs, one could at the same time update the documentation.
Is there a reason for the current situation?

The issue does not name documentation files, tests, or the current documentation repository. Start by identifying where the documentation currently lives and how documentation changes are proposed today. Done would require a maintainer decision on repository placement and a defined migration or organizational plan.

Vom Indexierungsmodell aus dem Issue-Text verfasst.