backlink added

Author: collaboratewithakash

core-java-11/README.md

@@ -2,4 +2,4 @@
 
 - [Java 11 Single File Source Code](https://www.baeldung.com/java-single-file-source-code)
 - [Java 11 Local Variable Syntax for Lambda Parameters](https://www.baeldung.com/java-var-lambda-params)
-
+- [Java 11 String API Additions](https://www.baeldung.com/java-11-string-api)