[FIX] doc: implement delegation/inheritance in JS documenter

Else website_sale_wishlist.wishlist blows up the documenter:
``events`` is set to sAnimations.Class.events but that is not an "own
property" of sAnimation.Class, it is instead inherited from Widget.

If delegation is not implemented, the value resolves to <nothing>,
which blows up when trying to set its name to the "property name" (by
calling ``set_name``).