astral-sh/ruff#18207 added a hint to the unresolved-import diagnostic, suggesting users to correctly configure their venv. While useful, I think we could do better by:

• Adding a note (or sub diagnostic?) explaining where ty searched for said import (which search paths are configured?)
  • first-party (if any): src.root
  • third-party: enviroment.python: Ideally, with an information how we detected said environment and how they could customize it
  • extra search paths (if any)
  • standard library (typeshed path)
• Add a note if there's no third-party import search path, hinting users to how they can configure it

I'm not sure how the best rendering looks like. You'll have to do some exploration on how to query and present the information to the user, so that it's useful.

We should also replace the URL to the documentation and use a redirect (I can set this up)