#1113 Link uml-reverse-mapper created class diagrams to readme, where needed

observer/README.md

@@ -19,6 +19,7 @@ Define a one-to-many dependency between objects so that when one
 object changes state, all its dependents are notified and updated
 automatically.
 
+## Class diagram
 ![alt text](./etc/observer.png "Observer")
 
 ## Applicability