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/AntergosNeXT/index.theme

@@ -0,0 +1,14 @@
+[Desktop Entry]
+Type=X-GNOME-Metatheme
+Name=Antergos NeXT
+Comment=Antergos NeXT custom theme
+Encoding=UTF-8
+
+[X-GNOME-Metatheme]
+GtkTheme=AntergosNeXT
+MetacityTheme=AntergosNeXT
+IconTheme=breeze-dark
+CursorTheme=breeze_cursors
+
+[GTK 3.0]
+Modules=color-renderer