Error-Checking In Preview Window for Customizable OpenSCAD Objects

This library implements an "assert" feature with a difference: rather than displaying
a console error, it actually renders 3D text of your choice describing the assertion
failure.
This is particularly useful for customizable (parameterized) SCAD files, where you want
a user to be able to customize the parameters on Thingiverse or in the OpenSCAD
application's Customizer pane. Your parameters may have limitations that can't be
expressed in customizer syntax, so you may be doing parameter-ch