title: How to use create-react-app build with custom enviroment variables?
body: <p>I have some custom enviroment variables for example:
  <code>REACT_APP_API_URL='http://localhost:6000/api'</code></p>
  
  <p>... and different enviroments (<code>develop</code>, <code>test</code>, <code>uat</code> and <code>production</code>).</p>
  
  <p>How can I define custom <strong>variables</strong> and custom <strong>build command</strong> for each enviroment?</p>
  
  <p>I found <a href="https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md#adding-development-environment-variables-in-env" rel="nofollow noreferrer">this CRA documentation</a> but it works with Node variables.</p>