fix: add export to interface for Watcher

[multivoltage]

A simple code like this in ts project:

import watch from "node-watch";

export const MyWatcher = function(){
  return watch("src")
}

generate this type error:
Exported variable 'MyWatcher' has or is using name 'Watcher' from external module "/Users/me/Documents/me-project/node_modules/node-watch/lib/watch" but cannot be named.

I try to fix it

[multivoltage]

Can I have an update?

[ghost]

Sorry I haven't had my old laptop with me for a while, and it may take a few more months :(

[multivoltage]

So can you merge this?