Add SheetDragNotifications

[Zabadam]

I'm looking at double closeProgressThresholdand I'm wondering about something similar for a drag gesture on same axis in opposite direction.

If the user can drag down to close Modal, could he or she drag upwards to expose or push a new Modal or view?

[petrnymsa]

Any progress on this?

We use nested navigator within modal and if user "drags" out modal, we want to completely close modal, not just pop() to previous nested page.