Feature request: move project to TypeScript

[xiaoxiangmoe]

APIDom is using TypeScript now and rely this minim's type.

https://github.com/swagger-api/apidom/blob/c9c85cfa99655203d62eaabe83b8bec09bbbd277/packages/%40types/minim.d.ts

Should we improve types support for this project? I'd be happy to do this.

[smizell]

@kylef could you and I talk about this? It would be good to discuss change and getting it into npm.