thinkpads: fix t480 monitor order

hosts/thinkpads/hardware-configuration.nix

@@ -36,4 +36,22 @@
 
   nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
   hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+
+  services.xserver.xrandrHeads = [
+    {
+      output = "HDMI-2";
+      monitorConfig = ''
+        Option "LeftOf" "eDP-1"
+        Option "PreferredMode" "1920x1200"
+      '';
+    }
+    {
+      output = "eDP-1";
+      monitorConfig = ''
+        Option "RightOf" "HDMI-2"
+        Option "PreferredMode" "1920x1200"
+      '';
+      primary = true;
+    }
+  ];
 }