Add troubleshooting FAQ to central location

E.g. clearing the cache comes up as a solution for many failing queries (and we need to point it out somewhere where it's super easily findable), also there are other reasonably frequent issues, e.g. not using the latest release (==> at least we need to point to the changelog so users get into the habit of checking that whether there was any updates to their modules), and changing row limit, etc.

So I would suggest adding a section to the index page, somewhere very central.

Start by locating the documentation index page and reviewing how central guidance is organized, then check the changelog and existing troubleshooting material. Done means a prominent FAQ section covers cache clearing, release updates, row limits, and other frequent query issues without leaving the suggested topics hard to find.

Written by the indexing model from the issue text.