title: How can I add a list to a user in firebase?
body: <p>I have an app I'm building.</p>
  
  <p>Right now the database looks like this.</p>
  
  <p><a href="https://i.stack.imgur.com/f0N72.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/f0N72.png" alt="Right now the database looks like this."></a></p>
  
  <p>I want to add to each of the users (When they first sign in) another field name "friends" and hold a list in there.
  How can I do it?</p>
  
  <p>I want it to be like this:</p>
  
  <p><a href="https://i.stack.imgur.com/YkLaE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YkLaE.png" alt="enter image description here"></a></p>