Move PipeWire configuration into own file

Also add link to documentation.

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" ];
+}