title: warning in react-router dom when user tries to navigate away from the site
body: <p>I have a multistep wizard with each step a react-router route.</p>
  
  <p>Currently if the user navigates away to an external link, they lose all their state.</p>
  
  <p>Is there a catch all in react-router-dom or react-router where I can warn the user and allow them to cancel?</p>