issue#6 fix php 7.4 compatible errors

Author: B24io

src/Users/DTO/Email.php

@@ -27,7 +27,7 @@ final class Email
     public function __construct(string $email)
     {
         $email = strtolower($email);
-        $this->username = implode(explode('@', $email, -1), '@');
+        $this->username = implode('@', explode('@', $email, -1));
         $this->domain = str_replace($this->username . '@', '', $email);
     }