PolyEllipse2D node

[Xrayez]

Goost has various CSG-like 2D nodes by now, such as recently implemented PolyCapsule2D: #134. However, it would be nice to implement other 2D primitives.

I've recently had an idea to create PolyEllipse2D node. I realize that PolyCircle2D could be used for that purpose by manipulating scale property. Yet the problem is that the distribution of points will no longer be uniform (see rough "staircase" edges):

Therefore, it would be nice to implement a dedicated class for this. GoostGeometry2D.ellipse() could also be added to return ellipse vertices closely approximating an ellipse shape.

I leave this as an idea for implementation for now. If someone would like to work on this, welcome!