Improve dragging into application

We don't receive any dragging events when items are dragged over Qt application on WASM now.
The events could be fired - but only with item types available in mime data as items are in protected mode when dragging.
See https://html.spec.whatwg.org/multipage/dnd.html#the-drag-data-store + https://html.spec.whatwg.org/multipage/dnd.html#dndevents