title: Import firebase/app used to work now I got error (firestore is not a function)?
body: <p>I am using React and Redux.
  I imported firebase using import shown below:</p>
  
  <pre><code>import * as firebase from 'firebase/app'
  import 'firebase/firestore'
  </code></pre>
  
  <p>Everything was working then I committed changes and pushed them to GitHub. My colleague pulled the code and told me to test it and it was not working. I tried to run the code but not working.
  I changed the import to:</p>
  
  <pre><code>import * as firebase from 'firebase/firebase'
  import 'firebase/firestore'
  </code></pre>
  
  <p>the code is working now.
  If anyone has an idea what is the reason for this error can you please help me to understand this issue.</p>