title: firebase docs reference grecaptcha but never import or define it
body: <p>From <a href="https://firebase.google.com/docs/auth/web/phone-auth" rel="noreferrer">https://firebase.google.com/docs/auth/web/phone-auth</a>:</p>
  
  <blockquote>
    <p>If signInWithPhoneNumber results in an error, reset the reCAPTCHA so
    the user can try again:</p>
  
  <pre><code>grecaptcha.reset(window.recaptchaWidgetId);
  
  // Or, if you haven't stored the widget ID:
  window.recaptchaVerifier.render().then(function(widgetId) {
    grecaptcha.reset(widgetId);
  }
  </code></pre>
  </blockquote>
  
  <p>But <code>grecaptcha</code> is never defined. Do I have to import it from somewhere?</p>