query search doc

[marc-vdm]

Checklist

• fix product database query search documentation needs examples #1519

• Keep pull requests small so they can be easily reviewed.

• Update the documentation

  • For in-code documentation, please follow the numpy style guide.
  • For user documentation, please update the wiki in
    ./activity_browser/docs/wiki

• Update tests.

• Link this PR to related issues by using closing keywords.

If you have write access (otherwise a maintainer will do this for you):

• Categorize the PR by setting a good title and adding one of the labels:
  bug, feature, ui, change, documentation, breaking, ci
  as they show up in the changelog.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.