Add renovate and knip support

From @ilyabo based on sqlrooms experience
I followed the advice from Tom MacWright about adding Knip and Renovate:
Knip is definitely very helpful to detect unused deps/files and also finds missing deps in packages.
Renovate, I think, is useful too: aside from getting improvements, for new adopters it's easier if we don't depend on old package versions. This way it's more "compatible" when you start a new project.
So far, we've only published prereleases with the updates from Renovate.
But I'd say, bump level should depend on what kind of dependency it is. If it's just a build tool not used at runtime then it can be a patch. If it's something that can alter runtime behavior, then it's different.
We'll be holding off some crucial deps, like e.g. arrow, because duckdb still depend on v17
here's Renovate makes a nice overview: https://github.com/sqlrooms/sqlrooms/issues/230

No files or tests are named. Start by locating the repository's dependency manifests and CI or configuration entry points, then determine how Knip and Renovate should be introduced and how runtime versus build-only updates are treated. Done means both tools are configured and the dependency-bump policy is explicit.