message: add redirect url OAuth2 to documentation
  Updated OAuth2 documentation to include redirect url examples
diff: @@ -49,6 +49,9 @@ To use this authentication scheme you will need to override following 2 fields i
  }
  }
  ```
  +<b> `Redirect Url` </b> : Used by OAuth supported endpoints to share the tokens with VSTS. Here's the callback url in TFS that should be used for redirection.
  +- TFS : http://yourhostname:8080/tfs/DefaultCollection/_admin/oauth2/callback
  +- Hosted (VSTS) : https://youraccount.visualstudio.com/_admin/oauth2/callback
  E.g below is how `oauth2` authentication scheme is used in *Github Enterprise* endpoint :
  ```
  