title: Create Firebase notification with page in foreground/focus
body: <p>With Firebase Cloud Messaging (for web), how can I generate the notification that appears when the webpage is closed or in the background, but when I'm actually focused on the webpage? </p>
  
  <p>It's my understanding that <code>messaging.onMessage(...)</code> is where I handle incoming messages when the page is in focus, but I can't seem to find documentation on how I could still create the notification pop-ups as though the page were in the background. </p>
  
  <p>Thanks for your time!</p>