title: Setting homepage as a variable in package.json and make it change conditionally
body: <p>How do I change/update <code>homepage</code> automatically without changing <code>package.json</code> in a React app?</p>
  <p>I have A and B project, both projects have individual roots for Production Build, but they share a same root for Test Build. That's why I have different <code>homepage</code> configured for different environments. When I merge its Test Branch to its Prod Branch, I have to keep the <code>package.json</code> file different, which is not smart at all.</p>
  <p>So, are there any ways that I can grab an Env variable and pass in?</p>