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

subclass-sandbox/README.md

@@ -12,6 +12,9 @@ tags:
 ## Intent  
 The subclass sandbox pattern describes a basic idea, while not having a lot of detailed mechanics. You will need the pattern when you have several similar subclasses. If you have to make a tiny change, then change the base class, while all subclasses shouldn't have to be touched. So the base class has to be able to provide all of the operations a derived class needs to perform.
   
+## Class diagram
+![alt text](./etc/subclass-sandbox.urm.png "Subclass Sandbox pattern class diagram")
+  
 ## Applicability  
 The Subclass Sandbox pattern is a very simple, common pattern lurking in lots of codebases, even outside of games. If you have a non-virtual protected method laying around, you’re probably already using something like this. Subclass Sandbox is a good fit when: