isValidKey using toArray() directly

Now it doesn't need to use toArray()->array_keys->in_array, but just toArray() and isset[$key], which should be faster.

Author: KKKas

src/Enum.php

@@ -119,7 +119,7 @@ public static function isValid($value)
      */
     public static function isValidKey($key)
     {
-        return in_array($key, self::keys(), true);
+        return isset(self::toArray()[$key]);
     }
 
     /**