add lmms module

TODO

@@ -1 +0,0 @@
-add lmms when it's working upstream

modules/nix/audio/default.nix

@@ -2,5 +2,6 @@
 {
   imports = [
     ./pipewire.nix
+    ./lmms.nix
   ];
 }

modules/nix/audio/lmms.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+let
+  inherit (lib) mkIf mkOption types;
+in
+{
+  options.smayzy.lmms.enable = mkOption {
+    type = types.bool;
+    default = false;
+    description = "lmms";
+  };
+
+  config = mkIf config.smayzy.lmms.enable {
+    environment.systemPackages = with pkgs; [ lmms ];
+  };
+}