[mintnet-kubernetes] add rancher as an option for DO [ci skip]

mintnet-kubernetes/docs/SETUP_K8S_ON_DO.md

@@ -4,10 +4,12 @@ Available options:
 
 1. [kubeadm (alpha)](https://kubernetes.io/docs/getting-started-guides/kubeadm/)
 2. [kargo](https://kubernetes.io/docs/getting-started-guides/kargo/)
-3. [terraform](https://github.com/hermanjunge/kubernetes-digitalocean-terraform)
+3. [rancher](http://rancher.com/)
+4. [terraform](https://github.com/hermanjunge/kubernetes-digitalocean-terraform)
 
 As you can see, there is no single tool for creating a cluster on DO.
 Therefore, choose the one you know and comfortable working with. If you know
 and used [terraform](https://www.terraform.io/) before, then choose it. If you
 know Ansible, then pick kargo. If none of these seem familiar to you, go with
-kubeadm.
+kubeadm. Rancher is a beautiful UI for deploying and managing containers in
+production.