title: export 'firestore' (imported as 'firebase') was not found in 'firebase' after upgrading to firebase js sdk v8
body: <p>I have upgraded the firebase JS SDK from v7 to v8.0.0 and I am importing firebase like so.</p>
  <pre><code>import * as firebase from 'firebase';
  </code></pre>
  <p>Accessing any of the following causes the error below.</p>
  <pre><code>firebase.firestore.FieldValue.serverTimestamp()
  firebase.User
  firebase.auth.UserCredential
  </code></pre>
  <blockquote>
  <p>export 'firestore' (imported as 'firebase') was not found in
  'firebase'
  Property 'firestore' does not exist on type 'typeof
  import(&quot;appPath/node_modules/firebase/index&quot;)'</p>
  </blockquote>
  <p>I have found a workaround by changing firebase to firebase.default e.g.</p>
  <pre><code>firebase.default.firestore.FieldValue.serverTimestamp()
  </code></pre>
  <p><strong>Is this the correct approach to resolve this?</strong></p>
  <p>EDIT: I am also using AngularFire in the project.
  I tried using:</p>
  <pre><code>import firebase from 'firebase/app';
  import 'firebase/firestore';
  export const firestore = firebase.firestore();
  </code></pre>
  <p>But this gave me the following error:</p>
  <blockquote>
  <p>Uncaught FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been
  created - call Firebase App.initializeApp() (app/no-app).</p>
  </blockquote>