Add azure kafka function sample

- Add sample project with Azure KafkaTrigger and Output Kakfa Bindings
 - Add README docs

 Resolves #836

spring-cloud-function-samples/function-sample-azure-kafka-trigger/src/main/resources/docker-compose-demo.yaml

@@ -0,0 +1,63 @@
+version: '2.1'
+
+services:
+  zookeeper:
+    image: zookeeper:3.4.9
+    hostname: zookeeper
+    ports:
+      - "2181:2181"
+    environment:
+      ZOO_MY_ID: 1
+      ZOO_PORT: 2181
+      ZOO_SERVERS: server.1=zookeeper:2888:3888
+    # volumes:
+    #   - ./zk-single-kafka-single/zookeeper/data:/data
+    #   - ./zk-single-kafka-single/zookeeper/datalog:/datalog
+
+  kafka1:
+    image: confluentinc/cp-kafka:7.2.2
+    hostname: kafka1
+    ports:
+      - "9092:9092"
+    environment:
+      KAFKA_ADVERTISED_LISTENERS: LISTENER_DOCKER_INTERNAL://kafka1:19092,LISTENER_DOCKER_EXTERNAL://${DOCKER_HOST_IP:-127.0.0.1}:9092
+      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: LISTENER_DOCKER_INTERNAL:PLAINTEXT,LISTENER_DOCKER_EXTERNAL:PLAINTEXT
+      KAFKA_INTER_BROKER_LISTENER_NAME: LISTENER_DOCKER_INTERNAL
+      KAFKA_ZOOKEEPER_CONNECT: "zookeeper:2181"
+      KAFKA_BROKER_ID: 1
+      KAFKA_LOG4J_LOGGERS: "kafka.controller=INFO,kafka.producer.async.DefaultEventHandler=INFO,state.change.logger=INFO"
+      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
+    # volumes:
+    #   - ./zk-single-kafka-single/kafka1/data:/var/lib/kafka/data
+    depends_on:
+      - zookeeper
+
+
+  init-kafka:
+    image: confluentinc/cp-kafka:7.2.2
+    depends_on:
+      - kafka1
+    entrypoint: [ '/bin/sh', '-c' ]
+    command: |
+      "
+      # blocks until kafka is reachable
+      kafka-topics --bootstrap-server kafka1:19092 --list
+
+      echo -e 'Creating kafka topics'
+      kafka-topics --bootstrap-server kafka1:19092 --create --if-not-exists --topic trigger --replication-factor 1 --partitions 1
+      kafka-topics --bootstrap-server kafka1:19092 --create --if-not-exists --topic output --replication-factor 1 --partitions 1
+
+      echo -e 'Successfully created the following topics:'
+      kafka-topics --bootstrap-server kafka1:19092 --list
+      "
+      
+  kconsole:
+    image: docker.redpanda.com/vectorized/console:latest
+    restart: on-failure
+    hostname: kconsole
+    ports:
+    - "8080:8080"
+    environment:
+      KAFKA_BROKERS: "kafka1:19092"
+    depends_on:
+      - kafka1