Update README.md

Author: kgiszewski

AbstractFactory/README.md

@@ -5,3 +5,5 @@ Super similar to the [Simple Factory](../SimpleFactory/README.md) except the `.C
 
 ## Common Uses
 The advantage over the Simple Factory is that this only depends on an abstraction whereas the Simple Factory depends on a concrete class.
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+Check out a video I made on factories: https://www.youtube.com/watch?v=qzxp9p7UP_Y