Recreate hello world working example with 5.0.95

[luerhard]

Maybe a disclaimer at first: I am very new to javascript and this is my first time playing around with Zotero.

To get used to the internal Javascript API, i rewrote the Hello World Example to get it to work with version 5.0.95 (standalone).

Regardless whether or not you accept this PR, Feedback is greatly appreciated - keep up the good work!

Best, Lukas