Customizable NEMA Stepper Mount

As I was not able to find a stepper motor mount that fulfilled all my needs, I've created my own version. Default settings fit my heavily modified CR10 S4. Belt hight is 23mm over the extrusion. Please use the customizer to configure your own mount. You should be able to make it fit to all 20mm based profiles, like the common 2020/2040 vslot used by Creality.

The OpenSCAD MCAD library is needed and - if you want a nice display - the [Build Plate library for OpenSCAD](https://www.thingiverse.com/thing:44094).