Function release_drag_on_unpress 

pub fn release_drag_on_unpress(
    commands: Commands<'_, '_>,
    pointer: Res<'_, PointerState>,
    released: Query<'_, '_, (Entity, &DragState), Without<Pressed>>,
    ends: MessageWriter<'_, DragEndEvent>,
)

On Pressed -> not-Pressed: remove DragState; if it was Active, emit DragEndEvent with the final pointer position.