Added link to demo video

doc/user/project/pages/pages_access_control.md

@@ -11,6 +11,9 @@ You can enable Pages access control on your project, so that only
 [members of your project](../../permissions.md#project-members-permissions)
 (at least Guest) can access your website:
 
+<i class="fa fa-youtube-play youtube" aria-hidden="true"></i>
+For a demonstration, see [Pages access controls](https://www.youtube.com/watch?v=tSPAr5mQYc8).
+
 1. Navigate to your project's **Settings > General** and expand **Visibility, project features, permissions**.
 1. Toggle the **Pages** button to enable the access control.