Add Mac-specific helper comment to step 1

Author: mikemclin

01 - Navigation/02 - Navigate to Declaration/2.1. Go to declaration.php

@@ -16,7 +16,7 @@
 $name = 'Hadi';
 $age = 53;
 
-// 1. Ctrl+Click on the Customer symbol
+// 1. Ctrl+Click (or Command+Click on Mac) on the Customer symbol
 // 2. Use the keyboard shortcut
 // 3. Go to Declaration for the $age variable passed into the below constructor
 $person = new Customer($name, $age);