Added: DDD link

docs/useCases.md

@@ -1,6 +1,6 @@
 # Use Cases
 
-In the context of Domain-Driven Design (DDD), a use case is a specific way to describe and capture a user's or system's interaction with the domain to achieve a particular goal. 
+In the context of [Domain-Driven Design (DDD)](https://martinfowler.com/bliki/DomainDrivenDesign.html), a use case is a specific way to describe and capture a user's or system's interaction with the domain to achieve a particular goal. 
 
 This package exposes the functionality in the form of use cases, with the main goal that any package consumer can easily identify the desired functionality.