Formatted snippets

Consistency in headings.

snippets/RGB-to-hexadecimal.md

@@ -1,4 +1,4 @@
-## RGB to hexadecimal
+### RGB to hexadecimal
 
 Convert each value to a hexadecimal string, using `toString(16)`, then `padStart(2,'0')` to get a 2-digit hexadecimal value.
 Combine values using `join('')`.

snippets/greatest-common-divisor-(GCD).md

@@ -1,4 +1,4 @@
-## Greatest common divisor (GCD)
+### Greatest common divisor (GCD)
 
 Use recursion.
 Base case is when `y` equals `0`. In this case, return `x`.