Update README.md

Author: kgiszewski

Observer/README.md

@@ -10,3 +10,7 @@ The observer pattern is a great way to decouple specifics from a core\engine.
 The observer pattern can be used to broadcast important steps of an execution to other classes. For instance when a long running process begins\ends, you could broadcast these events and act upon them by updating Slack.
 
 By doing so the core code (observable) wouldn't have to know anything about Slack, only the observing class would.
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+## Demo
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+I've created a video demo of the Observer Pattern that you can have a peek at here: https://www.youtube.com/watch?v=DgGKt0YgIBY&feature=youtu.be