Fixing HexValidator

> Fatal error: Uncaught InvalidArgumentException: Please make sure bytecode is valid.

I was getting the above error when I was trying to deploy my contract. Even though my bytecode is valid, it was failing the test

I fixed the code to use `ctype_xdigit` instead of regular express test

src/Validators/HexValidator.php

@@ -23,9 +23,6 @@ class HexValidator
      */
     public static function validate($value)
     {
-        if (!is_string($value)) {
-            return false;
-        }
-        return (preg_match('/^0x[a-fA-F0-9]*$/', $value) >= 1);
+        return is_string($value) && ctype_xdigit($value);
     }
-}
+}