Added gameplay YouTube link

UE4_TechDemos/ZombieShootout/README.md

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 Zombie Shootout is a single player 3rd person shooter. You control a soldier in a random generated dungeon and you battle your way through unlimited waves of zombies. To survive you must make sure to take advantage of the various powerups (double damage, frost ammo, incendiary ammo, regular ammo, healtkits) that are also spawned inside the dungeon - but be aware! After every wave the zombies stats increase! You can debuff the zombies by using two main debuffs: slow or damage over time. Each effect will cancel the other one. Inside the dungeon you can find healthkits which are either instant heal or over-time heal and double damage buffs which last for some seconds.
 
+https://www.youtube.com/watch?v=OtvDNKxoi7Q
+
 Main Fields:
 - Gameplay Programming (C++)
 - AI Programming (C++)