Update releases.json to include v1.8.1
Update releases.json to include v1.8.1

dlorenc/minikube,warmchang/minikube,warmchang/minikube,warmchang/minikube,kubernetes/minikube,warmchang/minikube,dlorenc/minikube,dlorenc/minikube,dlorenc/minikube,kubernetes/minikube,kubernetes/minikube,dalehamel/minikube,kubernetes/minikube,kubernetes/minikube,dalehamel/minikube,dlorenc/minikube,warmchang/minikube,dalehamel/minikube,dlorenc/minikube,dlorenc/minikube,warmchang/minikube,dlorenc/minikube,warmchang/minikube,kubernetes/minikube,kubernetes/minikube