Update README.md

Author: lor6

mapstruct/README.md

@@ -12,3 +12,5 @@ This module contains articles about MapStruct.
 - [Use Mapper in Another Mapper with Mapstruct and Java](https://www.baeldung.com/java-mapstruct-nested-mapping)
 - [Throw Exception for Unexpected Input for Enum With MapStruct](https://www.baeldung.com/java-mapstruct-enum-unexpected-input-exception)
 - [How to Use Conditional Mapping With MapStruct](https://www.baeldung.com/java-mapstruct-bean-types-conditional)
+- [Mapping Enum With MapStruct](https://www.baeldung.com/java-mapstruct-enum)
+