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.)
How about something like this (either replacing the switch statement or in addition before/after a reduced switch statement):
```
if ( types[i].indexOf("Conference Papers")>0) {
   return "conferencePaper";
} else if ( types[i].indexOf("Dissertation")>0 ) {
   return "thesis";
} else if (types[i].toLowerCase().indexOf("report")>0 ) {
   return "report";
} else if (types[i].indexOf("Book")>0) {
   return "book";
}
```