Fix OpenSCAD Dark Theme and other wrong GTK / QT styles on Garuda Linux (probably arch as well)

gistfile1.txt

Super easy fix - first, install qt5ct and do a test openscad launch like this:

```
QT_STYLE_OVERRIDE=qt5ct-style openscad
```

Instead of `qt5ct-style` you can use any of your own installed styles (some examples might be: kvantum-dark, kvantum, Fusion)
Which styles are installed you can check by running `qt5ct` or use kvantum as theme and then choose theme in kvantummanager.

Might work with some other apps GTK/QT apps, too.

To make it permanent you can:
1. Edit system launcher for OpenSCAD and replace it with `env QT_STYLE_OVERRIDE=qt5ct-style openscad %f`
2. Or add it to permanent config script globally like that:
```
export QT_STYLE_OVERRIDE=qt5ct-style
```

Might work as well on Manjaro and other Arch spinoffs.

1. Install qt5ct:

sudo pacman -S qt5ct

2. Check that theme is dark by running qt5ct and verifying it in GUI.

3. Run openscad with dark theme via qt5ct:

QT_QPA_PLATFORMTHEME=qt5ct openscad