Add fields to the citation editor

[Futur3r]

Is your feature request related to a problem? Please describe.
To contribute references directly in the citation tab, it would be great to be able to put all of the key used translated by the Wikidata Quickstatement translator. These key are also the basis of good metadata for citing.

Describe the solution you'd like
Adding the fields issue, volume, pages, numPages, edition, url, langid (see #222), extra and cito to the citation editor.

Also, the Citiation Typing Ontology (cito) (see #163) could be added this way. With a certain value of the key cito that would be later interpreted by the translators.

The values could just be the english labels of the cito wikidata elements or if there is an issue of language the values could be directly their QID's.
Or the values could be added via a drop down menu (like for auhtors or item types), so there would be the possibility to translate every value via Translate Wiki. But the drop down needs to have like a search bar where you can start to fill the name of the cito to go faster.

Describe alternatives you've considered
Creating items in the "library view" of Zotero and after having contribute them in Wikidata, adding them as citations of an item with a manual export/import in BibLaTeX.