Suggest using DNS instead of kube-api on README

[ignasi35]

REAMDE.md explains how an implementation of an Akka Discovery mechanism is necessary and uses Kubernetes-API as an example. I think in production users are unlikely to use Kubernetes-API for service-to-service discovery and we should use a production ready example like DNS

[TimMoore]

I think it would make sense to provide a default via play/reference-overrides.conf that configures the aggregate method with configuration first, and then DNS. This should be a suitable default for almost everyone, and only people with truly custom service registries should need to customize this.

[TimMoore]

Note that those methods are all part of the core Akka Discovery module, and don't require additional dependencies.