add some darwin user stuff

modules/darwin/user.nix

@@ -0,0 +1,13 @@
+{ pkgs, ... }: {
+
+  users.users."${user}" = { # macOS user
+    home = "/Users/${user}";
+    shell = pkgs.zsh; # Default shell
+  };
+
+  networking = {
+    computerName = "MacBook"; # Host name
+    hostName = "MacBook";
+  };
+
+}