Add deep dive YouTube id to reverse-string (#2365)

Author: iHiD

exercises/reverse-string/metadata.toml

@@ -2,3 +2,4 @@ title = "Reverse String"
 blurb = "Reverse a given string."
 source = "Introductory challenge to reverse an input string"
 source_url = "https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb"
+deep_dive_youtube_id = "AzLWkOZLYGM"