Add dwm window manager with some initial patches

- Set Mod4 as the mod key and Alacritty as the termcmd.
- Add a patch from suckless.org to hide any vacant tags.
  - https://dwm.suckless.org/patches/hide_vacant_tags

nix/hosts/t490/services/default.nix

@@ -1,11 +1,10 @@
-{ ... }:
-
 {
   imports = [
+    ./dwm.nix
     ./interception-tools.nix
     ./sound.nix
-    ./xserver.nix
     ./udev.nix
+    ./xserver.nix
   ];
 
   services = {

nix/hosts/t490/services/dwm.nix

@@ -0,0 +1,27 @@
+{ pkgs, ... }:
+
+{
+  services = {
+    dwm-status = {
+      enable = true;
+
+      order = [
+        "audio"
+        "backlight"
+        "battery"
+        "cpu_load"
+        "network"
+        "time"
+      ];
+    };
+
+    xserver.windowManager.dwm.enable = true;
+  };
+
+  environment.systemPackages = with pkgs; [
+    dmenu
+    dmenu-bluetooth
+    networkmanager_dmenu
+    st
+  ];
+}