Checks added so that Zotero standalone notes can be exported.

[sohamm17]

Checks if an item is a regular item, then only certain functions are fully executed. Also fixes so that creating a mdnote or standalone md note works for Zotero standalone note (a Zotero note without any parent note).

[argenos]

Hi @sohamm17, thanks for the contribution! Before I merge this, can you tell me a little about what was the bug you were trying to fix?