Complete Antergos NeXT custom theme with cross-DE support

- Custom GTK3/GTK4/GTK2 theme (AntergosNeXT) with blue #2EA3F2 accent
- KDE Plasma color scheme matching the theme
- dconf overrides for GNOME/Cinnamon/Budgie/Deepin
- XFCE xfconf defaults for theme/icon/font
- GTK settings.ini for all GTK-based DEs
- /etc/skel defaults for new users

packages/antergos-next-desktop-settings/gtk-settings.ini

@@ -0,0 +1,6 @@
+[Settings]
+gtk-font-name=Noto Sans, 10
+gtk-icon-theme-name=breeze-dark
+gtk-theme-name=Breeze-Dark
+gtk-cursor-theme-name=breeze_cursors
+gtk-application-prefer-dark-theme=1