Export options types for encode/decode

[grantila]

If I want to write a wrapper around encode() or decode() (and the other), I might want to forward the types needed for these functions, e.g. EncodeOptions. But to reach this type I need to import

import { EncodeOptions } from "@msgpack/msgpack/dist/encode"

...which is kindof ugly. I don't want to import from a dist/ folder, that's a technical detail that may change in the future.

It would be great if these types which are implicitly exposed, would also be explicitly exported in the index file.