title: Running custom NPM commands in parallel and timing
body: <p>I'm wanting to use Google Lighthouse NPM package however unlike all their examples which run against a public URL, I'm wanting to use it on my localhost.</p>
  
  <p>Question is, I need to run the NPM scripts in the following order which is what I'm struggling with:</p>
  
  <ol>
  <li>Run my dev server script (runs create-react-app dev server and runs localhost:3000)</li>
  <li>Wait until server is up and running</li>
  <li>Keep dev server running and run the Google Lighthouse NPM script against localhost:3000</li>
  <li>Once Google Lighthouse has finished doing it's audits then kill the dev server.</li>
  </ol>
  
  <p>All a question of either manual timings or if something can use a callback. Also need to consider two tasks running at the same time.</p>