Add reference to arXiv preprint based on published DOI

[marcusps]

It is possible to search the arXiv by DOI, so for entries that include a DOI, it would be great to search the arXiv for the corresponding preprint, and to add the appropriate corresponding fields (such as archivePrefix, eprint, primaryClass, following https://info.arxiv.org/help/hypertex/bibstyles/index.html).