Variants in FreeCAD: Prototype Variant Parts with Configurations

This video shows the prototype from [this earlier video](https://spectra.video/w/oSf2mydXr4WySDrJcgS2j5) how configurations could work with these Variant Parts. In the video I reimplement a nut defined in the video ["SolidWorks Configuration Tables with Equations"](https://www.youtube.com/watch?v=JSOsL9kQyfk) by [Dan Abbott](https://www.youtube.com/@DanAbbott-SMCC/featured). I use VarSets to define various configurations similar to in Dan Abbott's video. Note that I did not implement all of the design, but just the parts to show the principle.