Consider supporting the `rusoto_dynamodbstreams` crate

[jakejscott]

Hi @softprops

Sorry to keep sending you feature requests :) I should look into contributing myself!

I've noticed that the rusoto_dynamodbstreams has the same types generated like AttributeValue etc.

Wondering if it would be worth while trying to support serializing those types also?

Happy to try and look into it (as manual parsing is really difficult)