Add AppVeyor status to root README.md

Author: SteveSandersonMS

README.md

@@ -1,5 +1,7 @@
 # JavaScriptServices
 
+AppVeyor: [![AppVeyor](https://ci.appveyor.com/api/projects/status/gprilrckx116vc9m/branch/dev?svg=true)](https://ci.appveyor.com/project/aspnetci/javascriptservices/branch/dev)
+
 This project is part of ASP.NET Core. You can find samples, documentation and getting started instructions for ASP.NET Core at the [Home](https://github.com/aspnet/home) repo.
 
 ## What is this?