title: how to add files in web.config transformation process?
body: <p>I am having a website developed in Visual Studio 2012.
  The web.config is currently containing following files in its transformation:
  - web.Debug.config
  - web.Release.config</p>
  
  <p>I have recently added a new build configuration (named as "Staging") in my project. How can I create a "web.Staging.config" transformation file?</p>