- fix spelling

stacks/arraystack/arraystack.go

@@ -137,7 +137,7 @@ func (stack *Stack) String() string {
 	return str
 }
 
-// Check that the index is withing bounds of the list
+// Check that the index is within bounds of the list
 func (stack *Stack) withinRange(index int) bool {
 	return index >= 0 && index < stack.list.Size()
 }