Wrap the MenuListItem widget with a LongPressDraggable widget.

In this case, when the user long presses on the
MenuListItem widget, the LongPressDraggable
widget displays a DraggingListItem.
This DraggingListItem displays a photo of the
selected food item, centered beneath 
the user’s finger.

The dragAnchorStrategy property is set to
pointerDragAnchorStrategy.
This property value instructs LongPressDraggable
to base the DraggableListItem’s position on the 
user’s finger. As the user moves a finger,
the DraggableListItem moves with it.

Dragging and dropping is of little use if no information
is transmitted when the item is dropped.
For this reason, LongPressDraggable takes a data parameter. 
In this case, the type of data is Item,
which holds information about the 
food menu item that the user pressed on.