Write documentation on best practices for researcher DB access

[hellais]

During the review of the OONI Data & Systems Usage Policy document it came up that:

Maybe at some point it would be a good idea to add a "good practices" section with this kind of thing
@LDiazN

It would be great to write this up as part of a document inside of docs.ooni.org: https://github.com/ooni/data/blob/main/.github/workflows/build_docs.yml
also: https://docs.ooni.org/meta/
and https://docs.ooni.org/meta/#how-documentation-is-built