feat: Theming integration

[tulilirockz]

The planned idea is to have themes work this way:

• Gnome: Bluefin-like theme, because that proved to work quite well + some audio extensions and whatever else might be useful
• Plasma: Ubuntu Studio-like theme with our own spin, like a different accent colors, and something else I havent planned yet

Ill be trying to make a "unified" theme on these two desktops so that Atomic Studio has a "visual identity". The theming will be: Papirus Icon Theme + Helvetica Neue + Materia Theme + some other gradience tweaks