title: Limit Firebase Google OAuth Authentication to specific users
body: <p>I'm using Firebase to handle my Google OAuth login for my website. Does anyone knew how to restrict the users who have access to the application? For example, I only want x@gmail.com, y@gmail.com, and z@gmail.com to successfully be able to log in via google to my application. </p>
  
  <p>I wasn't sure if this was a Firebase or Google question, but any help would be much appreciated.</p>