create startChatContact lambda diagram and add WAF notes (#165)

#153

cloudformationTemplates/startChatContactAPI/README.md

@@ -1,6 +1,10 @@
 # Overview
 
-Adding chat to your website is possible with a few easy steps. This solutions spins up an [Amazon API Gateway](https://aws.amazon.com/api-gateway/) endpoint that triggers an [AWS Lambda](https://aws.amazon.com/lambda/) function. This Lambda function invokes the [Amazon Connect](https://aws.amazon.com/connect/) Service [StartChatContact](https://docs.aws.amazon.com/en_pv/connect/latest/APIReference/API_StartChatContact.html) API and returns the result from that call. Once you have the StartChatContact API you can either pass that response to the prebuilt widget to get a quick implementation going or you can build your own customer chat experience by using the [Amazon Connect Chat JS]( https://github.com/amazon-connect/amazon-connect-chatjs)  library. 
+Adding chat to your website is possible with a few easy steps. This solutions spins up an [Amazon API Gateway](https://aws.amazon.com/api-gateway/) endpoint that triggers an [AWS Lambda](https://aws.amazon.com/lambda/) function. This Lambda function invokes the [Amazon Connect](https://aws.amazon.com/connect/) Service [StartChatContact](https://docs.aws.amazon.com/en_pv/connect/latest/APIReference/API_StartChatContact.html) API and returns the result from that call. Once you have the StartChatContact API you can either pass that response to the prebuilt widget to get a quick implementation going or you can build your own customer chat experience by using the [Amazon Connect Chat JS]( https://github.com/amazon-connect/amazon-connect-chatjs)  library.
+
+> ⚠️ This sample code does not come with built in security. It is highly recommended to implement [AWS WAF](https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-control-access-aws-waf.html) for the API Gateway.
+
+!["Diagram"](./images/StartChatContactArchitecture.png)
 
 ## CloudFormation Deployment Steps