Add a reference to reddit thread on tabs vs space discussion

Author: mathdebate09

foundations/javascript_basics/clean_code.md

@@ -148,7 +148,7 @@ You might wonder why this variable is declared with all caps when we recommended
 
 ### Indentation and line length
 
-Now it's time to head to more controversial topics. The war between coders that use tabs and coders that use spaces to indent their code is essentially a joke by now.
+Now it's time to head to more controversial topics. The war between coders that use tabs and coders that use spaces to indent their code is essentially a [joke](https://www.reddit.com/r/programming/comments/p1j1c/tabs_vs_spaces_vs_both/) by now.
 
 What actually matters is *consistency*. Choose a way to indent and stick to it. Various JavaScript style guides recommend different options, and one is not really superior to the other. We will look at style guides and related tools in more detail later in the curriculum.