Add a usage section to the readme

[olizilla]

This looks rad, but how do I run it?

I read the docs at https://cluster.ipfs.io/documentation/guides/k8s/ and set some secrets but I had to guess at what to run. Sure, I'm a k8s noob, but so are lots of folks. I tried a $ kubectl apply -k . from one of the overlay dirs but got an error...

❖ ~/Code/lanzafame/ipfs-cluster-k8s/overlays/basic-auth-example on master* 
$ kubectl apply -k .
configmap/env-config created
configmap/ipfs-cluster-set-bootstrap-conf created
secret/secret-config created
service/ipfs-cluster created
error: error validating ".": error validating data: [ValidationError(StatefulSet.spec.volumeClaimTemplates[0].spec): unknown field "persistentVolumeReclaimPolicy" in io.k8s.api.core.v1.PersistentVolumeClaimSpec, ValidationError(StatefulSet.spec.volumeClaimTemplates[1].spec): unknown field "persistentVolumeReclaimPolicy" in io.k8s.api.core.v1.PersistentVolumeClaimSpec]; if you choose to ignore these errors, turn validation off with --validate=false

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.6", GitCommit:"96fac5cd13a5dc064f7d9f4f23030a6aeface6cc", GitTreeState:"clean", BuildDate:"2019-08-19T11:13:49Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.6", GitCommit:"96fac5cd13a5dc064f7d9f4f23030a6aeface6cc", GitTreeState:"clean", BuildDate:"2019-08-19T11:05:16Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}

[suutaku]

same problem