pipewire: Add pulseaudio

This is necessary so we can load the module-switch-on-connect module,
which makes switching between USB audio devices automatic among other
things.

desktop/pipewire/default.nix

@@ -1,3 +1,5 @@
+{ pkgs, ... }:
+
 {
   services.pipewire = {
     enable = true;
@@ -12,5 +14,9 @@
     lowLatency.enable = true;
   };
 
+  environment.systemPackages = with pkgs; [
+    pulseaudio
+  ];
+
   security.rtkit.enable = true;
 }