Publish types for API with npm release

[humphd]

Description

I'm using the API version of serve in TypeScript, and it complains about not having type info. I notice that you've updated the code to use TypeScript, and I wondered if you'd consider publishing types as well for people using it programmatically.

Why

I think for people working in TS and using the API version, this is really needed.

Alternatives

I looked for alternate types on Definitely Typed, but couldn't find them (maybe I'm missing something).