Feature Request: Export `Mux` when generating typescript server

[fangyi-zhou]

Hello team,

We're using Smithy TypeScript server code generator for an AWS lambda function, and it's been working greatly. We've recently encountered a use case where we're trying to write an authorizer lambda for the lambda function that is dependent on the HTTP path. We've noticed that the default code generation provides a Mux inside get$OPERATIONHandler and get$SERVICEHandler, and it looks like we can reuse the Mux for implementing our authorizer lambda. Is it possible to export the Mux in a separate function?

Thanks!