Prepare release v0.19.0 and bump chart version (#689)

Author: baluchicken

charts/kafka-operator/Chart.yaml

@@ -4,4 +4,4 @@ version: 0.4.13
 description: kafka-operator manages Kafka deployments on Kubernetes
 sources:
   - https://github.com/banzaicloud/koperator
-appVersion: v0.18.3
+appVersion: v0.19.0