Transition Cell Types for Volume Meshes

[mgsutton]

Once again, thanks for the great library! I noticed the docs say that volume meshes can support hexes and tets, and even a mixture of the two. For the latter case using polyscope::registerTetHexMesh, how does that work for transition cells between the two types? Are wedges and pyramids specified as degenerate hex cells, or are they just currently not supported? If they aren't supported, it sure would be great if they could be.