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/azure/host.json

@@ -0,0 +1,16 @@
+{
+    "functionTimeout": "00:05:00",
+    "version": "2.0",
+    "extensions": {
+        "kafka": {
+            "maxBatchSize": 64,
+            "SubscriberIntervalInSeconds": 1,
+            "ExecutorChannelCapacity": 1,
+            "ChannelFullRetryIntervalInMs": 50
+        }
+    },
+    "extensionBundle": {
+        "id": "Microsoft.Azure.Functions.ExtensionBundle",
+        "version": "[3.3.0, 4.0.0)"
+    }
+}

spring-cloud-function-samples/function-sample-azure-kafka-trigger/src/main/azure/local.settings.json

@@ -0,0 +1,12 @@
+{
+	"IsEncrypted": false,
+	"Values": {
+		"AzureWebJobsStorage": "UseDevelopmentStorage=true",
+		"AzureWebJobsDashboard": "",
+		"FUNCTIONS_WORKER_RUNTIME": "java",
+
+		"BrokerList": "localhost:9092",
+		"ConfluentCloudUsername": "test",
+		"TriggerKafkaTopic": "trigger"
+	}
+}