Hanger for Aerobies, boomerangs and ring-like objects

This is a customizable hanger allowing you to concentrically hang ring-like objects like Aerobies. By default, the outermost holder is for the official Aerobie Pro. The middle one is for a [200mm flying ring](https://www.thingiverse.com/thing:2641936). And the smallest one is for some boomerangs.

Uses and bundles my [tubemesh](https://www.thingiverse.com/thing:2406760) library.