Toothpaste tube joiner: Crest <--> Crest

Joins a Crest toothpaste tube to a Crest toothpaste tube.

OpenSCAD: https://github.com/pconwell/3d-models/blob/main/toothpaste/joiner_crest.scad

Original design joined two cap piece designs together.

This design is much simpler, smaller, and quicker to print. The design will hold the two ends of the tubes together, so there should be nothing to clean.