Add udev rules for Keychron C2

Without these, the function keys don’t work as function keys, but only
as media keys.

base/default.nix

@@ -7,5 +7,6 @@
         ./packages.nix
         ./users.nix
         ./locale.nix
+        ./hardware.nix
     ];
 }

base/hardware.nix

@@ -0,0 +1,7 @@
+{ pkgs, ... }:
+{
+    services.udev.extraRules = ''
+        # Keychron C2 function key fix
+        SUBSYSTEMS=="input", ATTRS{name}==Keychron C2", RUN+="${pkgs.coreutils}/bin/echo 0 | ${pkgs.coreutils}/bin/tee /sys/module/hid_apple/parameters/fnmode"
+    '';
+}