add desmume

modules/nix/emulator/default.nix

@@ -0,0 +1,6 @@
+{ ... }:
+{
+  imports = [
+    ./desmume.nix
+  ];
+}

modules/nix/emulator/desmume.nix

@@ -0,0 +1,20 @@
+{
+  lib,
+  config,
+  pkgs,
+  ...
+}:
+let
+  inherit (lib) mkIf mkOption types;
+in
+{
+  options.smayzy.desmume.enable = mkOption {
+    type = types.bool;
+    default = false;
+    description = "enable desmume";
+  };
+
+  config = mkIf config.smayzy.desmume.enable {
+    environment.systemPackages = with pkgs; [ desmume ];
+  };
+}