(Maybe large?) Feature Request: Add support for dp.la

[HalosGhost]

dp.la has a huge library of public-domain works well-formatted, available in a very pleasant interface, and via an API. Given how open it is, maybe it would be easy to integrate support for, but I suspect this isn't a light lift.

Any interest? I'd love to be able to have both sources easily-available right on the rm2.