Add support for Amazon MSK events

[ewbankkit]

Is your feature request related to a problem? Please describe.
AWS Lambda now supports Amazon Managed Streaming for Apache Kafka (Amazon MSK) as an event source.
Announcement: https://aws.amazon.com/about-aws/whats-new/2020/08/aws-lambda-now-supports-amazon-managed-streaming-for-apache-kafka-as-an-event-source/.
Event format: https://docs.aws.amazon.com/lambda/latest/dg/with-msk.html#services-msk-configure.