re-add nuget package in readme (#469)

Author: zhiyuanliang-ms

README.md

@@ -1,5 +1,8 @@
 # .NET Feature Management
 
+[![Microsoft.FeatureManagement](https://img.shields.io/nuget/v/Microsoft.FeatureManagement?label=Microsoft.FeatureManagement)](https://www.nuget.org/packages/Microsoft.FeatureManagement)
+[![Microsoft.FeatureManagement.AspNetCore](https://img.shields.io/nuget/v/Microsoft.FeatureManagement.AspNetCore?label=Microsoft.FeatureManagement.AspNetCore)](https://www.nuget.org/packages/Microsoft.FeatureManagement.AspNetCore)
+
 Feature management provides a way to develop and expose application functionality based on features. Many applications have special requirements when a new feature is developed such as when the feature should be enabled and under what conditions. This library provides a way to define these relationships, and also integrates into common .NET code patterns to make exposing these features possible. 
 
 ## Get started