Update README.md

Added introductory blurb at the beginning.

Author: ebruersan

samples/manage/sql-assessment-api/README.md

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-# SQL Assessment API samples
+# SQL Assessment API
+
+SQL Assessment API provides a mechanism to evaluate the configuration of your SQL Server for best practices. The API is delivered with a ruleset containing best practice rules suggested by SQL Server Team. This ruleset is enhancing with the release of new versions but at the same time, the API is built with the intent to give a highly customizable and extensible solution. So, users can tune the default rules and create their own ones. The API can be used to assess SQL Server versions 2012 and higher and Azure SQL Database Managed Instance (more to come).
+
+Learn more about the API on the [SQL Assessment API docs page](https://docs.microsoft.com/en-us/sql/sql-assessment-api/sql-assessment-api-overview).
 
-Contains samples for customizing SQL Assessment API. Learn more about the API on the [SQL Assessment API docs page](https://docs.microsoft.com/en-us/sql/sql-assessment-api/sql-assessment-api-overview).
 
 ## QuickStart.md