Update README.md

Add build badge

Author: commonsensesoftware

README.md

@@ -1,5 +1,6 @@
 [![.NET Foundation](https://img.shields.io/badge/.NET%20Foundation-blueviolet.svg)](https://dotnetfoundation.org/projects/aspnet-api-versioning)
 [![MIT License](https://img.shields.io/github/license/dotnet/aspnet-api-versioning?color=%230b0&style=flat-square)](https://github.com/dotnet/aspnet-api-versioning/blob/main/LICENSE.txt)
+[![Build Status](https://dev.azure.com/aspnet-api-versioning/build/_apis/build/status/dotnet.aspnet-api-versioning.old?branchName=ms)](https://dev.azure.com/aspnet-api-versioning/build/_build/latest?definitionId=3&branchName=ms)
 
 | :mega: Check out the [announcement](../../discussions/807) regarding upcoming changes |
 |-|