Distance to surface for ellipsoids

[tommy-waltmann]

Feature description

I would like to get the distance to the surface of the shape for ellispoids

Proposed solution

add a distance_to_surface method for ellipsoids

Additional context

The distance_to_surface method was added for many 2D shapes a while ago in #141 (#136 #137 #140 are related issues), but that PR didn't handle any 3D shapes. There are analytical equations for the surface of an ellipsoid, so it should be pretty quick to add this.