Update README.md

Author: AnghelLeonard

HibernateSpringBootMergeCollections/README.md

@@ -6,3 +6,5 @@
      - Remove the existing database rows that are no longer found in the incoming collection\
      - Update the existing database rows which can be found in the incoming collection\
      - Add the rows found in the incoming collection, which cannot be found in the current database snapshot
+     
+<a href="https://leanpub.com/java-persistence-performance-illustrated-guide"><p align="center"><img src="https://github.com/AnghelLeonard/Hibernate-SpringBoot/blob/master/Java%20Persistence%20Performance%20Illustrated%20Guide.jpg" height="410" width="350"/></p></a>