title: firebase-admin with typescript in firebase cloud functions
body: <p>I am using firebase cloud functions with javascript on cloud functions.
  And, I want to switch from javascript to typescript.</p>
  
  <p>However I cannot use firebase-admin on typescript as following command failed.</p>
  
  <pre><code>command: npm install @types/firebase-admin --save-dev
  error:  '@types/firebase-admin' is not in the npm registry.
  </code></pre>
  
  <p>According to this release note, it looks that firebase admin support typescript.
  Can somebody tell us how to use typescript with firebase-admin on cloud functions?</p>
  
  <p><a href="https://firebase.google.com/support/release-notes/admin/node#4.1.3" rel="noreferrer">https://firebase.google.com/support/release-notes/admin/node#4.1.3</a></p>