Mention the necessity of lambda:InvokeFunction permission in lazy listener document #267

As mentioned in this feedback, the lazy listener guide for AWS Lambda users should clearly mention the required IAM policy.

The reason why I went with my own IAM role is that lazy listener function feature invokes async AWS lambda functions from a lambda function. If you use this functionality, you need to add lambda:InvokeFunction permission to your app.

This should be noted in the docs as you cannot test with chalice local when using lazy listeners. Chalice logs a 500 error as boto throws a botocore.errorfactory.ResourceNotFoundException... or worse, it invokes whatever is at function:api_handler.

Originally posted by @jlujan-invitae in #162 (comment)