Update releases.json to include v0.28.1
Update releases.json to include v0.28.1

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