modules: add sound

I will probably want to share this configuration between multiple
machines in the future.

modules/default.nix

@@ -12,6 +12,7 @@
     ./networking.nix
     ./nix.nix
     ./packages.nix
+    ./sound.nix
     ./upower.nix
     ./users.nix
   ];

modules/sound.nix

@@ -0,0 +1,25 @@
+{ config, lib, ... }:
+let
+  cfg = config.my.modules.sound;
+in
+{
+  options.my.modules.sound = with lib; {
+    enable = mkEnableOption "sound configuration";
+
+    pulse = {
+      enable = mkEnableOption "pulseaudio configuration";
+    };
+  };
+
+  config = lib.mkIf cfg.enable (lib.mkMerge [
+    # Basic configuration
+    {
+      sound.enable = true;
+    }
+
+    # Pulseaudio setup
+    (lib.mkIf cfg.pulse.enable {
+      hardware.pulseaudio.enable = true;
+    })
+  ]);
+}