undo container doc

Author: cephalin

articles/app-service/quickstart-custom-container.md

@@ -20,6 +20,7 @@ This quickstart shows how to deploy an ASP.NET app, in a Windows image, to [Dock
 
 To complete this tutorial:
 
+- <a href="https://hub.docker.com/" target="_blank">Sign up for a Docker Hub account</a>
 - <a href="https://docs.docker.com/docker-for-windows/install/" target="_blank">Install Docker for Windows</a>.
 - <a href="/virtualization/windowscontainers/quick-start/quick-start-windows-10" target="_blank">Switch Docker to run Windows containers</a>.
 - <a href="https://www.visualstudio.com/downloads/" target="_blank">Install Visual Studio 2019</a> with the **ASP.NET and web development** and **Azure development** workloads. If you've installed Visual Studio 2019 already: