Add a build badge for Azure Pipelines

This will show the commit test status of the master branch as reported by Azure Pipelines.

README.md

@@ -23,7 +23,7 @@ text file.
 
 ## Building and Installing Rakudo
 
-[![Build Status](https://circleci.com/gh/rakudo/rakudo.svg?style=shield)](https://circleci.com/gh/rakudo/rakudo)[![Build Status](https://travis-ci.org/rakudo/rakudo.svg?branch=master)](https://travis-ci.org/rakudo/rakudo) [![Build Status](https://ci.appveyor.com/api/projects/status/github/rakudo/rakudo?svg=true)](https://ci.appveyor.com/project/rakudo/rakudo/branch/master)
+[![Build Status](https://dev.azure.com/Rakudo/rakudo/_apis/build/status/rakudo.rakudo?branchName=master)](https://dev.azure.com/Rakudo/rakudo/_build/latest?definitionId=1&branchName=master) [![Build Status](https://circleci.com/gh/rakudo/rakudo.svg?style=shield)](https://circleci.com/gh/rakudo/rakudo)[![Build Status](https://travis-ci.org/rakudo/rakudo.svg?branch=master)](https://travis-ci.org/rakudo/rakudo) [![Build Status](https://ci.appveyor.com/api/projects/status/github/rakudo/rakudo?svg=true)](https://ci.appveyor.com/project/rakudo/rakudo/branch/master)
 
 See the `INSTALL.txt` file for detailed prerequisites and build and
 installation instructions.