Citable resources

[ChasNelson1990]

The landing pages in the repository include metadata required for citation of the resources and are in machine-readable format

The file download URL is available, and we have the "short URLs" extension, but this should be improved to include citation examples and ensure it is all machine readable.

Relates #17

[A-Souhei]

ckanext-scheming and ckanext-dcat could be used here.

ckanext-shorturl does not seem to exist anywhere?

[ChasNelson1990]

I think @tomeksabala can tell us where the short URLs feature is (I am guessing ckanext-unaids) but we should think about adding an extra layer here to have both human (https://citation.js.org/) and machine (DCAT) readable metadata and citations