Add arXiv to preprint metrics

[virginiascarlett]

Would it be possible/reasonable to add arXiv to the "Preprint DOI institutions" pie chart on https://dis.int.janelia.org/dois_preprint? I think you'd need to sift out arxiv DOIs in one of two ways. Either dig into the DataCite metadata and look for ["identifiers"]["identifierType"] == "arXiv", like so: "identifiers": [ { "identifier": "2406.17936", "identifierType": "arXiv" } ], Or just do a regex to search for the substring "arxiv" in the DOI itself.

[virginiascarlett]

A couple of recent arXiv DOIs for practice: 10.48550/arXiv.2405.12385, 10.48550/arxiv.2406.17936