Update README.md

Author: codejava-official

README.md

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 Project code for Spring Boot REST API Request Validation Examples
 ### Follow our written tutorial here: [Spring Boot REST API Request Validation Examples](https://www.codejava.net/frameworks/spring-boot/rest-api-request-validation-examples)
 ### Watch coding in action on YouTube: [Spring Boot REST API Request Validation Examples](https://www.youtube.com/watch?v=eX8Wr5MeEnw)
+## Learn more about Spring framework:
+### [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)