title: Notification API - Ask permission after denied
body: <p>Is it possible to request permission to send push notifications again after user has clicked "Block" instead of "Allow" or closing the popup?</p>
  
  <p>Simply running <code>Notification.requestPermission();</code> doesnt't trigger the permission request popup anymore.</p>
  
  <p><code>Notification.permission</code> returns <code>"denied"</code></p>