Added increment explanation + completed 1-count.js

Author: codebyshay

Sprint-1/1-key-exercises/1-count.js

@@ -4,3 +4,8 @@ count = count + 1;
 
 // Line 1 is a variable declaration, creating the count variable with an initial value of 0
 // Describe what line 3 is doing, in particular focus on what = is doing
+// This line (line 3), is updating the value of the count variable. The = operator is an assignment 
+// operator which assigns the value on the right (count + 1) to the variable on the left (count). 
+// count = count + 1;
+// This operation is called increment.
+// An increment means increasing the value of a variable by 1.