Add support for browser usage in npm package

[redeemedfadi]

• See https://docs.npmjs.com/files/package.json#browser

In order to use this library in both a node environment and the browser, we should add a browser entry into package.json. Webpack and other build systems can read the entry and choose the correct file based on the target.

[crhistianramirez]

@redeemedfadi this is now released under version 2.0.1