thinkpad/x1-extreme/gen3: add module

lenovo/thinkpad/x1-extreme/gen3/default.nix

@@ -0,0 +1,19 @@
+{ lib, ... }:
+
+{
+  imports = [
+    ../.
+  ];
+
+  # New ThinkPads have a different TrackPoint manufacturer/name.
+  hardware.trackpoint.device = "TPPS/2 Elan TrackPoint";
+
+  # Fix clickpad (clicking by depressing the touchpad).
+  boot.kernelParams = [ "psmouse.synaptics_intertouch=0" ];
+
+  # Set the right DPI. xdpyinfo says the screen is 677x423 mm but
+  # it actually is 344×215 mm.
+  services.xserver.monitorSection = lib.mkDefault ''
+    DisplaySize 344 215
+  '';
+}