Signature stamp holder

Model is printed upright with handle facing up. It should import into your slicer without need for rotating.

OnShape model can be [found here](https://cad.onshape.com/documents/ccd0a2dfafb04cd346a8b7de/w/3e188d0536aab45d077c4b61/e/71d75302960c5c99dc88b85f).

The size of your stamp that you insert into the holder should be about `15.6mm x 8.5mm x 6.4mm` (width, depth, height). The height of the holder is roughly based on this: [Speedball's soft carving block](http://a.co/3Tc8ALK). If your st