Drawer: Support anchoring on Item

The "Drawer" Control currently is anchored at the window edge. It would be nice if it was possible to set its parent to a different Item to e.g have it on an edge of a "Page".

This would allow having multiple Drawers that are related to the content of the current view, and not the whole application.

My current workaround is writing a new component using a Popup that clips a swipeable ListView item to emulate the Behavior of a Drawer. It's quite inconvenient and fragile, as these controls weren't really made for this use.