Add literature citation

[juliettelavoie]

If the experiment CVs include the doi of the appropriate MIP paper to cite, this could also be added to the bibtex file. We could also add the CMIP Overview paper if we decide it is required (WCRP-CMIP/cmip7-guidance#30).

[juliettelavoie]

@ngks89 also suggests an option to add model description papers. For CMIP7, we might be able to get this from the Essential Model Documentation..