Add Bazzite configs and README

Copy Niri, btop, glow, GTK, xsettingsd, environment.d and autostart
configs from Bazzite machine. Add README with project structure and
setup instructions for both macOS and Bazzite.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bazzite/gtk-4.0/gtk.css

@@ -0,0 +1,2 @@
+@import 'colors.css';
+@import 'kde_window_geometry.css';