Common style/appearance cross platform

[nightsky30]

Common style/appearance cross platform

• Stylesheets

Different styles per platform:
https://stackoverflow.com/questions/43424794/is-there-a-way-to-enable-qss-stylesheets-parts-per-os

Dark theme stuff:
https://stackoverflow.com/questions/48256772/dark-theme-for-in-qt-widgets
https://github.com/ColinDuquesnoy/QDarkStyleSheet
https://github.com/Alexhuszagh/BreezeStyleSheets

Stylesheets:
https://doc.qt.io/qt-5/stylesheet-syntax.html#