Add dynamic script loader

[cleverbeagle]

Wrote a tutorial on this but it seems worth the inclusion! https://cleverbeagle.com/blog/articles/tutorial-how-to-load-third-party-scripts-dynamically-in-javascript

export default (url, library, callback) => {
  const existingScript = document.getElementById('scriptId');

  if (!existingScript) {
    const script = document.createElement('script');
    script.src = url; // URL for the third-party library being loaded.
    script.id = library; // e.g., googleMaps or stripe
    document.body.appendChild(script);

    script.onload = () => {
      if (callback) callback();
    };
  }

  if (existingScript && callback) callback();
};