The DrawFeature control can be used to digitize donut polygons.
                To digitize holes in polygons, hold down the Alt 
                key and draw over an existing polygon.  By default, the 
                Shift key triggers freehand drawing.  Use a 
                combination of the Shift and Alt keys
                to digitize holes in freehand mode.
            
See the donut.js source for details on how this is done.