docs: add diagrams for event aggregator, event-based asynchronous, event queue, execute around, extension objects

event-based-asynchronous/README.md

@@ -32,6 +32,10 @@ In Plain Words
 
 > The Event-Based Asynchronous design pattern allows tasks to be executed in the background, notifying the main program via events when completed, thereby enhancing system efficiency and responsiveness without blocking ongoing operations.
 
+Sequence diagram
+
+![Event-Based Asynchronous sequence diagram](./etc/event-based-asynchronous-sequence-diagram.png)
+
 ## Programmatic Example of Event-Based Asynchronous Pattern in Java
 
 Event-Based Asynchronous design pattern allows tasks to be executed in the background, notifying the main program via events when completed, thereby enhancing system efficiency and responsiveness without blocking ongoing operations.