Mention network requirement in the README

Author: ralphbean

hack/new-cluster/README.md

@@ -23,6 +23,8 @@ This automation creates yaml files in the infra-deployments repo locally.
 * `env` - One of `production` or `staging`.
 * `network` - One of `public` or `private`.
 
+4. You are connected to the VPN.
+
 ## Procedure
 
 **Run the playbook**, which will prompt you for the five variables above: