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.)
I don't like splitting on comma. If you look above, that doesn't actually solve this for Dissertation or Conference Paper (where we may or may not now cover all cases). I think first matching on a regex for some key terms is the way to go.