Update ProQuest.js

See https://forums.zotero.org/discussion/40821/zotero-not-recognizing-books-chapters-dissertations-in-proquest-psycinfo/

(Maybe we should wait for more examples of different types.)
the order seems pretty random here. Since this is a tiny bit less efficient than switch (right?) I suggest we at least make some attempt to put common item types first: I'd suggest journal, newspaper, dissertation, book, chapter in that order; the rest shouldn't matter much.