Add penguin configuration

modules/nixos/my_nix/default.nix

@@ -0,0 +1,42 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.my_nix;
+  inherit (lib) mkEnableOption mkIf mkOption;
+  types = lib.types;
+in
+{
+  options.my_nix = {
+    enable = mkEnableOption "Custom nix options";
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ pkgs.cachix ];
+    nix = {
+      optimise = {
+        automatic = true;
+      };
+      settings = {
+        experimental-features = [
+          "nix-command"
+          "flakes"
+        ];
+        substituters = [
+          "https://nix-community.cachix.org"
+          "https://cache.nixos.org"
+        ];
+        trusted-public-keys = [
+          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+        ];
+      };
+    };
+    nixpkgs.config = {
+      allowUnfree = true;
+    };
+  };
+}