Blank extruder spinner (for MPSM et al)

Created the [Star of David](https://www.thingiverse.com/thing:3303258) extruder spinner for a friend, then created the [Goofball spinner](https://www.thingiverse.com/thing:3303297) off the same design, and as I was posting them, I realized that hey, maybe someone wants just the blank coin so they can add their own stuff.

If you use Fusion360, I've included the F3D file so you can just import that and have the full history. If you use another CAD program I've included IGES and STEP files so h