Context API

Obviously React is getting a new Context API, but you have to support more than 16.3 with Formik so you won't be able to use it. I [asked Dan Abramov on Twitter](https://twitter.com/dan_abramov/status/979079793110069249) and he recommended using [React Broadcast](https://github.com/ReactTraining/react-broadcast) to polyfill it for older versions. What about adding this to `formik-effect`/`formik` instead of using the old context api? The primary reason is this:

```js
const MyPureComponent extends React.PureComponent {
render() {
return this.props.children;
}
}

const MyForm = (props) => (
console.log(values)}
initialValues={{ firstName: '', lastName: '', email: '' }}
render={props =>


{
// This will never receive changes as PureComponent props never change
// and wont pass them down to their children
}}
/>




Submit

}
/>
);
```

Start by reviewing the formik-effect/formik integration and the React Broadcast approach described in the issue, with attention to support for React versions before 16.3. Done means Effect receives Formik state changes when nested beneath a React.PureComponent while preserving the stated older-version support.

Written by the indexing model from the issue text.