Update README.md

Author: rcalago

core-kotlin-modules/core-kotlin-design-patterns/README.md

@@ -9,3 +9,4 @@ This module contains articles about design patterns in Kotlin
 - [The Chain of Responsibility Pattern in Kotlin](https://www.baeldung.com/kotlin/chain-of-responsibility-pattern)
 - [The Adapter Pattern in Kotlin](https://www.baeldung.com/kotlin/adapter-pattern)
 - [The Facade Pattern in Kotlin](https://www.baeldung.com/kotlin/facade-pattern)
+- [The Visitor Pattern in Kotlin](https://www.baeldung.com/kotlin/visitor-pattern)