Update README.md

Author: codejava-official

README.md

@@ -6,3 +6,5 @@ Project code for Spring Boot REST API Request Validation Examples
 ### [Spring Framework Tutorials](https://www.codejava.net/spring-tutorials)
 ### [Spring Boot Tutorials](https://www.codejava.net/spring-boot-tutorials)
 ### [Spring Security Tutorials](https://www.codejava.net/spring-security-tutorials)
+## Mastering REST API development with Java and Spring:
+### [Spring Boot REST APIs Ultimate Course](https://www.udemy.com/course/spring-boot-rest-apis-ultimate/?referralCode=763F7EE87CECC337D708)