Perhaps fill that ellipsis in the README with a couple of methods.

[catamphetamine]

People are having difficulties with understanding how the polyfill actually works (what does it actually do).
gpbl/react-day-picker#685

Perhaps the README could be more descriptive about that, something like:

import React from 'react';
import {polyfill} from 'react-lifecycles-compat';

class ExampleComponent extends React.Component {
  getSnapshotBeforeUpdate(prevProps, prevState) { ... }
  static getDerivedStateFromProps(props, state) { ... }
  ...
}

// Polyfill your component so the new lifecycles will work with older versions of React:
polyfill(ExampleComponent);

export default ExampleComponent;

[bvaughn]

Done! e4e21a6

Thanks for pointing this out.