Add example use of zotero.iterate(since=) to FAQ

[andreifoldes]

Hello,

I think many user might be interested in using the zotero.iterate(since=) parameter and it would be worth giving an example of it to the FAQ.

If I understand correctly one can use zot.last_modified_version() to get a version of their entire library and then feed it into zotero.iterate(since=) to only process new items added to the library since the last time they've ingested?