Move PipeWire configuration into own file

Also add link to documentation.

config/hosts/audio/default.nix

@@ -4,6 +4,7 @@
     ./configuration.nix
     ./librespot.nix
     ./networking.nix
+    ./pipewire.nix
     ./shairport-sync.nix
   ];
 }

config/hosts/audio/pipewire.nix

@@ -0,0 +1,17 @@
+# Sources for this configuration:
+# - https://nixos.wiki/wiki/PipeWire
+
+{ config, pkgs, ... }:
+
+{
+  security.rtkit.enable = true;
+  services.pipewire = {
+    enable = true;
+    systemWide = true;
+    alsa.enable = true;
+    alsa.support32Bit = true;
+    pulse.enable = true;
+  };
+
+  users.users.chaos.extraGroups = [ "pipewire" ];
+}

config/hosts/audio/shairport-sync.nix

@@ -11,16 +11,7 @@
     arguments = "-o pw";
   };
 
-  security.rtkit.enable = true;
-  services.pipewire = {
-    enable = true;
-    systemWide = true;
-    alsa.enable = true;
-    alsa.support32Bit = true;
-    pulse.enable = true;
-  };
   users.users.shairport.extraGroups = [ "pipewire" ];
-  users.users.chaos.extraGroups = [ "pipewire" ];
 
   environment.etc.shairport-sync-config = {
     enable = true;