refactor: prepare for multi machine config

common/default.nix

@@ -0,0 +1,30 @@
+({ nixpkgs, ... }: {
+  # Select internationalisation properties.
+  i18n.defaultLocale = "en_CA.UTF-8";
+  console = {
+    keyMap = "ca";
+  };
+
+  nixpkgs.config.allowUnfree = true;
+
+  nix = {
+    # Edit nix.conf
+    settings = {
+      experimental-features = [ "nix-command" "flakes" ];
+      keep-outputs = true;
+      keep-derivations = true;
+      auto-optimise-store = true;
+      warn-dirty = false;
+    };
+
+    # Minimize dowloads of indirect nixpkgs flakes
+    registry.nixpkgs = {
+      flake = nixpkgs;
+      exact = false;
+    };
+  };
+
+  imports = [
+    ./overlays/list.nix
+  ];
+})