Export of creator-type fields from embedded CSL variables + change authors to directors for CSL-JSON film+tvBroadcast + export tvBroadcast to biblatex video

citeproc-js recognizes {:label: lastName || firstName} in Zotero’s Extra field as a two-field name value. (See https://github.com/zotero/zotero/issues/846.)

BBT could use the same syntax (not too pretty, but then again, we don’t have to invent one from scratch).

This would be great to add creator types for items that don’t currently support them (e.g., “Director”¹ for “Film”, “Editor” for “Report” and “Web page”, …).

¹ Zotero does have a “Director” field but does not export it properly.