Add documentation

README.md

@@ -322,6 +322,7 @@ The settings exposed here are targeted to more advanced users that want to custo
 |LibkafkaDebug|debug|Both
 |MetadataMaxAgeMs|metadata.max.age.ms|Both
 |SocketKeepaliveEnable|socket.keepalive.enable|Both
+|EnableDeliveryReports|Feature of Confluent.Kafka|Output
 
 **NOTE:** `MetadataMaxAgeMs` default is `180000` `SocketKeepaliveEnable` default is `true` otherwise, the default value is the same as the [Configuration properties](https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md). The reason of the default settings, refer to this [issue](https://github.com/Azure/azure-functions-kafka-extension/issues/187).