gnome: Fix QT apps theme

modules/programs/gnome/default.nix

@@ -17,10 +17,14 @@
         gnome.gnome-terminal
         pinentry-gnome
         dconf # For home-manager
+        libsForQt5.qtstyleplugin-kvantum
       ];
       gnome.excludePackages = pkgs.gnome.optionalPackages;
+      sessionVariables = {
+        "QT_STYLE_OVERRIDE" = "kvantum";
+      };
     };
-
+    
     services = {
       accounts-daemon.enable = true;
       colord.enable = false;
@@ -65,6 +69,14 @@
     };
 
     home-manager.users."${config.system.singleUser}" = {
+      xdg.configFile = {
+        # Make QT apps use a dark theme
+        "Kvantum/kvantum.kvconfig".text = ''
+          [General]
+          theme=KvArcDark
+        '';
+      };
+
       dconf.settings = {
         # The packages come in from modules/programs/gnome
         # Theme