Add brightness control

hosts/thinkpads/home.nix

@@ -1,5 +1,6 @@
 { pkgs, ... }: {
   imports = [
     ./polybar.nix
+    ./i3.nix
   ];
 }

hosts/thinkpads/i3.nix

@@ -0,0 +1,12 @@
+{ pkgs, lib, ... }:
+
+{
+  home.packages = with pkgs; [
+    brightnessctl
+  ];
+
+  xsession.windowManager.i3.config.keybindings = lib.mkOptionDefault {
+    "XF86MonBrightnessUp" = "exec --no-startup-id brightnessctl set +5%";
+    "XF86MonBrightnessDown" = "exec --no-startup-id brightnessctl set 5%-";
+  };
+}