freecad: add support

[RANKSHANK]

Adds support for FreeCAD

base16/gruvbox-dark-hard

base16/catppuccin-latte

Works by generating a preference pack with a config file and a qss stylesheet that match the theme. This means users will need to select pack in FreeCAD's preferences menu. Changes will also only propagate after either cycling packs or restarting FreeCAD.

There are a lot of components getting themed here, many of which I've just 'best guessed' at for the first pass, so I'm opening this as a draft for input whilst I'm dog-fooding the changes.

Current Todo List:

• [x] Script/Macro editor implementation
• [ ] Disable the preference pack's generation when FreeCAD is not installed
• [ ] Investigate lightmode's color implementation
• [ ] Add an icon to the preference pack
• [ ] Migrate xml to nix generators
• [ ] General polish

[RANKSHANK]

Good point, added to the todo list, cheers