Support DOI references

[sopoforic]

I was writing a comment on #251 when I realized that I this is really a separate, but related issue:

It would be good if promnesia would support not just the URL from Zotero, but also the DOI (which is often in meta tags on web pages).

In an ideal world, if I have Citation Key: Miller1956 in the Extra field (because I use Better Bibtex for Zotero) and @Miller1956 in the :ROAM_REFS: key in an org file (because I use org-roam), and I visit the page with either the URL or DOI associated with that article in zotero, I'd like to see my org-roam notes. But I'd settle for duplicating the DOI in the org file, if I had to. And, of course, if I should have the DOI mentioned somewhere I'd expect that to show up in promnesia, same as a mention of the URL would.

That given, I could then open up the list of references in an article and have promnesia mark the ones I have in zotero etc. (by marking the DOI link, if present--no magic expected).

[karlicoss]

thanks! Yeah, would be nice to support at some point (few people asked for it before: https://beepb00p.xyz/exobrain/projects/cannon.html#stwttrcmmghjlhlsttsnrmlsd )