Adding docs for ReactorKafkaBinderHealthIndicator

See #2948

docs/modules/ROOT/nav.adoc

@@ -73,6 +73,7 @@
 **** xref:kafka/kafka-reactive-binder/multiplex.adoc[]
 **** xref:kafka/kafka-reactive-binder/pattern.adoc[]
 **** xref:kafka/kafka-reactive-binder/sender_result.adoc[]
+**** xref:kafka/kafka-reactive-binder/health_indicator.adoc[]
 *** Kafka Stream Binder
 **** xref:kafka/kafka-streams-binder/usage.adoc[]
 **** xref:kafka/kafka-streams-binder/overview.adoc[]

docs/modules/ROOT/pages/kafka/kafka-reactive-binder/health_indicator.adoc

@@ -0,0 +1,19 @@
+[[reactor-kafka-binder-health-indicator]]
+= Reactor Kafka Binder Health Indicator
+
+Reactor Kafka binder provides a `HealthIndicator` implementation that will be used when invoking the Spring Boot Actuator `health` endpoint.
+When Spring Boot actuator dependency is on the classpath, the Reactor Kafka binder can be enabled with a binder health indicator.
+This health indicator provides information about the status of the binder based application, i.e. if it is currently `UP` or `DOWN`, the topics in usage by the application, and the various details about the message producer components that the binder uses internally.
+
+
+The Reactor Kafka Binder Health Indicator is registered with the key `reactorKafka` internally by the framework.
+Therefore, it can be queried programmatically as shown below.
+
+[source, java]
+----
+CompositeHealthContributor compositeHealthContributor = context
+			.getBean("bindersHealthContributor", CompositeHealthContributor.class);
+ReactorKafkaBinderHealthIndicator healthIndicator = (ReactorKafkaBinderHealthIndicator) compositeHealthContributor.getContributor("reactorKafka");
+Health health = healthIndicator.health();
+----
+