added comment to fix for options1

exercises/option/option1.rs

@@ -12,6 +12,7 @@ fn main() {
     print_number(Some(99));
 
     let mut numbers: [Option<u16>; 5] = [None; 5]; // Issue #395 on rustlings
+// Using  [0; 5]; Will fail to compile as the types are mismatched. Therefore putting Some or None into the default values of the array as you initialize is important to understand.
     for iter in 0..5 {
         let number_to_add: u16 = {
             ((iter * 1235) + 2) / (4 * 16)