kitty: make extraConfig obey mkOrder

this change makes kitty.extraConfig obey the lib.mkOrder function so
that text can be inserted at the right place.

modules/programs/kitty.nix

@@ -12,6 +12,8 @@ let
     mkOption
     optionalString
     types
+    mkMerge
+    mkOrder
     ;
 
   cfg = config.programs.kitty;
@@ -275,32 +277,37 @@ in
 
     home.packages = [ cfg.package ] ++ optionalPackage cfg.font;
 
+    programs.kitty.extraConfig = mkMerge [
+      (mkIf (cfg.font != null) (
+        mkOrder 510 ''
+          font_family ${cfg.font.name}
+          ${optionalString (cfg.font.size != null) "font_size ${toString cfg.font.size}"}
+        ''
+      ))
+      (mkIf (cfg.themeFile != null) (
+        mkOrder 520 ''
+          include ${pkgs.kitty-themes}/share/kitty-themes/themes/${cfg.themeFile}.conf
+        ''
+      ))
+      (mkIf (cfg.shellIntegration.mode != null) (
+        mkOrder 530 ''
+          # Shell integration is sourced and configured manually
+          shell_integration ${cfg.shellIntegration.mode}
+        ''
+      ))
+      (mkOrder 540 (toKittyConfig cfg.settings))
+      (mkOrder 550 (toKittyActionAliases cfg.actionAliases))
+      (mkOrder 560 (toKittyKeybindings cfg.keybindings))
+      (mkOrder 570 (toKittyEnv cfg.environment))
+    ];
+
     xdg.configFile."kitty/kitty.conf" =
       {
-        text =
-          ''
-            # Generated by Home Manager.
-            # See https://sw.kovidgoyal.net/kitty/conf.html
-          ''
-          + lib.concatStringsSep "\n" [
-            (optionalString (cfg.font != null) ''
-              font_family ${cfg.font.name}
-              ${optionalString (cfg.font.size != null) "font_size ${toString cfg.font.size}"}
-            '')
-
-            (optionalString (cfg.themeFile != null) ''
-              include ${pkgs.kitty-themes}/share/kitty-themes/themes/${cfg.themeFile}.conf
-            '')
-            (optionalString (cfg.shellIntegration.mode != null) ''
-              # Shell integration is sourced and configured manually
-              shell_integration ${cfg.shellIntegration.mode}
-            '')
-            (toKittyConfig cfg.settings)
-            (toKittyActionAliases cfg.actionAliases)
-            (toKittyKeybindings cfg.keybindings)
-            (toKittyEnv cfg.environment)
-            cfg.extraConfig
-          ];
+        text = ''
+          # Generated by Home Manager.
+          # See https://sw.kovidgoyal.net/kitty/conf.html
+          ${cfg.extraConfig}
+        '';
       }
       // lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
         onChange = ''