Add deprecation notice on main readme (#657)

* Update README.adoc

Author: abhijeet2096-confluent

README.adoc

@@ -1,4 +1,4 @@
-= Confluent Platform Helm Charts
+= Confluent Platform Helm Charts [Deprecated]
 :icons: font
 :toc: auto
 :toc-placement: macro
@@ -12,6 +12,8 @@
 :source-highlighter: rouge
 :experimental:
 
+*Deprecated*: The cp-helm-charts is deprecated in favor of [Confluent For Kubernetes](https://docs.confluent.io/operator/current/overview.html) .
+
 You can use the Helm charts to deploy services on Kubernetes for development, test, and proof of concept environments.
 
 CAUTION: Open Source Helm charts are not supported by Confluent.