Document what happens if there are multiple entries in CITATION.bib

[oxinabox]

For a package that wraps a bunch of algorithms each published in there own papers,
I have always thought it makes sense to include those papers in the CITATION.bib,
after the one for the package itself.

WHat does Cite.jl do if it encounters such in the CITATION.bib

[SebastianM-C]

Right now Cite.jl includes all the references mentioned in the CITATION.bib in the generated file and in the default cite sentence.

If there would be a standard on how to structure the CITATION.bib file, we could use that for algorithms in the packages.
As mentioned in #1 (comment), and more detailed in #7 there could be a lightweight package used by Cite.jl and interested packages which would provide extra citation functionality.