Updated index.md of Reinforcement Learning (#19103)

Added info on AlphaGo and its significance. It is an important and widely used example, hence I have added it.

client/src/pages/guide/english/machine-learning/reinforcement-learning/index.md

@@ -16,6 +16,8 @@ A bot is given a task to play Space Invaders, it tries to learn to play it by in
 
 In industries robot uses deep reinforcement learning to pick a device from one box and putting it in a container. Whether it succeeds or fails, it memorizes the object and gains knowledge and train’s itself to do this job with great speed and precision. Learning on its own is a kind of reinforcement learning provided the learning is in positive dimension.
 
+The best example, and one which you will hear a lot in this field, is AlphaGo developed by Google. This uses reinforcement learning to learn the patterns, rules and semantics of the board game, Go. This bot defeated the World No. 1 Go player, Lee Sedol, in what was the first time a computer program defeated a professional player. AlphaGo won by 4-1 in a five game series. This was a huge victory for AI and kickstarted the field of Reinforcement learning. 
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 ## List of Common Algorithms
 Q-Learning
 Temporal Difference (TD)