Allows to generate ellipses by passing width and height.
Accuracy is much better for thin shapes. The circle shape can be scaled (see bottom shape), but this degrades accuracy. Using an ellipse shape is efficient in this regard because you don't have to make max_error extremely low to achieve the same accuracy that would lead to performance loss during boolean operations between other PolyNode2D-based shapes.
Solves #139.
widthandheight.max_errorextremely low to achieve the same accuracy that would lead to performance loss during boolean operations between otherPolyNode2D-based shapes.