Update README.md to make clear security hardening is not done for you. (#140)

Co-authored-by: Devin Buhl <onedr0p@users.noreply.github.com>

README.md

@@ -193,6 +193,8 @@ In order to use Terraform and `cert-manager` with the Cloudflare DNS challenge y
 
 :round_pushpin: Here we will be running a Ansible Playbook to prepare Ubuntu for running a Kubernetes cluster.
 
+:round_pushpin: Nodes are not security hardened by default, you can do this with [dev-sec/ansible-collection-hardening](https://github.com/dev-sec/ansible-collection-hardening) or something similar.
+
 1. Ensure you are able to SSH into you nodes from your workstation with using your private ssh key. This is how Ansible is able to connect to your remote nodes.
 
 2. Install the deps by running `task ansible:deps`