Deprecate other values than string for CreditCard

Test for card number `6304100000000008` fails on windows because a number this long can't be stored as an integer.
Instead it becomes a float and when converted into string it is 6.3041E+15 instead of 6304100000000008.

CreditCard::validate should only allow string arguments.

This is done in a BC way and should be updated for next major.

src/IsoCodes/CreditCard.php

@@ -20,6 +20,15 @@ class CreditCard implements IsoCodeInterface
      */
     public static function validate($creditCard)
     {
+        if (!is_string($creditCard)) {
+            @trigger_error(
+                'Passing other values than a string on '.__METHOD__.' is deprecated since version 2.2.'
+                .' It will be considered as invalid on version 3.0.',
+                E_USER_DEPRECATED
+            );
+        }
+
+        // Add !is_string($creditCard) to the condition on 3.0.
         if (trim($creditCard) === '') {
             return false;
         }