`FeatureDescription` type not exported in `react-enable` root

[felladrin]

Hi there, thanks for creating this lib!

While going through the example, I've noticed an issue in the Readme, which indicates we should import the lib like this:

react-enable/README.md

Line 23 in 0fc0542

import { Features, ToggleFeature, Disable, Enable, FeatureDescription } from 'react-enable';

But I was only able to import it using the following:

import { Features, ToggleFeatures, Disable, Enable } from "react-enable";
import { FeatureDescription } from "react-enable/dist/FeatureState";

FeatureDescription was not exported in react-enable root.

I also noticed that ToggleFeature component name is actually ToggleFeatures.