Turn stylesheet in to FreeCAD Preference Pack

[luzpaz]

See https://github.com/Chrismettal/FreeCAD-Behave-Dark-Preference-Pack

Edit: FreeCAD-Behave was added to the Addon Manager (see FreeCAD/FreeCAD-addons@0d23295)

ref: FreeCAD/FreeCAD-addons#201

[pgilfernandez]

Well, this Blender stylesheet is pretty old and outdated compared with the ones that were merged with FreeCAD master (and even updated a few times fixing some bugs and adding improvements). So the first thing for turning it now into a Preference Pack would be to fully update the stylesheet and then creating the pack.

I will do it when I can, but sadly it won't be soon...

[luzpaz]

We're close to a release of v0.20
Any time you can spare to update the stylesheet? 🙏