Add Azure Pipelines badge.

Author: BillyONeal

README.md

@@ -11,6 +11,8 @@ The C++ REST SDK is a Microsoft project for cloud-based client-server communicat
 [![openSUSE Tumbleweed package](https://repology.org/badge/version-for-repo/opensuse_tumbleweed/cpprestsdk.svg)](https://repology.org/metapackage/cpprestsdk)</br>
 [![Debian Testing package](https://repology.org/badge/version-for-repo/debian_testing/cpprestsdk.svg)](https://repology.org/metapackage/cpprestsdk)</br>
 
+[![Build Status](https://dev.azure.com/vclibs/cpprestsdk/_apis/build/status/Microsoft.cpprestsdk.Ubuntu)](https://dev.azure.com/vclibs/cpprestsdk/_build/latest?definitionId=1)
+
 With [vcpkg](https://github.com/Microsoft/vcpkg) on Windows
 ```
 PS> vcpkg install cpprestsdk cpprestsdk:x64-windows