Include index.d.ts in npm package

[NotWoods]

I added the index.d.ts file but forgot to include it in the "files" field in package.json, so its not distributed with the npm package.

@lukastaegert The typing file does not exists in the package available on npm registry.
I think this part is missing in package.json file :

"files": [
    "dist/*.js",
    "dist/*.d.ts"
  ],

And maybe also :

 "typings": "index.d.ts",

Originally posted by @nicolashenry in #363 (comment)

[lukastaegert]

Thanks a lot!