Support for org-ref v3

[dangom]

Hello,

I see that this mode is meant to work with org-cite. Do you think it'd be possible to tweak it to work with org-ref v3? (essentially changing @ to & in the references).
Asking because I don't know how much of the internal API depends on org-cite specific stuff.

[rougier]

In the latest version, there's no explicite dependency such that it may be compatible with org-cite or org-ref, based on the bib file only. I've started experiment with citar and it seems to work without too much trouble (not committed yet)