Resolve "Extend facet_grid plot to allow setting titles with a custom template"

This MR addresses #330 (closed) by adding the title_kwargs argument to the facet_grid plot functions.

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped

Related issues

Closes #330 (closed)