Feature to block the user of drawing at the canvas
I would like to know if there is already a feature that does not allow the user to draw on the canvas. For example, a ```canDraw``` property at ```ReactSketchCanvas``` that avoids the user to draw on it?

I'm developing a drawing game and I want to only allow the user to draw when it's his turn. I already kinda implemented it while I was checking the code, if this feature does not exist, I can add it.
