Whiteboard: Let the user draw freehand graphics on a page

This object lets the user draw freehand graphics on a page.

It can create a canvas object for the whiteboard (if one does not exist) and let the user draw on the canvas area by dragging the mouse around.

The color, thickness, line join and line cap of the drawing pen can be configured.

The object can also clear the whiteboard, export the coordinates of the drawn lines or import previously drawn lines.