Update readme.md

Author: pmasl

samples/manage/hdfs-kerberos-tester/readme.md

@@ -10,7 +10,7 @@ This tool is completely independent from SQL Server. It is available as a Jupyte
 
 - SQL Server 2016 RTM CU6 / SQL Server 2016 SP1 CU3 / SQL Server 2017 or higher with PolyBase installed
 - A Hadoop cluster (Cloudera or Hortonworks) secured with Kerberos (Active Directory or MIT)
-- Azure Data Studio
+- [Azure Data Studio](https://docs.microsoft.com/sql/azure-data-studio/download)
 - Around 40 MB of hard disk space
 
 ## Instructions