Support for CloudFront Lambda@Edge

Hi,

I've been using the aws-lambda-go package for integrating API Gateway, S3, DynamoDB and Lambda. It's been great!

One integration I'm really interested in using is CloudFront (Lambda@Edge). It would be great if the request/response types are modeled already so that I don't have to write the boilerplate.

ref; https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-generating-http-responses.html