Feature request: PolygonObstacle (2D), maybe MeshObstacle?

so from a representation perspective these should be easy, we can do polygons, we can do meshes

for the force laws, a Polygon would also be easy-ish — there are two cases that need to be treated separately, either you interact with an edge or with a vertex (i.e. two edges)

in 3D, there's already three cases — single face, two faces, or a vertex (arbitrarily many faces unless we artifically restrict mesh geometry)

anyway i have no intention of implementing this any time soon, but we can use this issue as a dumping ground for ideas in this direction