Update readme before archiving repo
Update readme before archiving repo

Development of CDK charms has moved to a new org (charmed-kubernetes). To prevent future writes to this fork, we'll archive it and make it read-only, potentially deleting it at some point in the future. Before archiving, this commit updates the readme to inform users where they can find the new stream of development for CDK.
juju-solutions/kubernetes,juju-solutions/kubernetes,juju-solutions/kubernetes,juju-solutions/kubernetes,juju-solutions/kubernetes,juju-solutions/kubernetes