add socket.io's handshake.auth option

[laszlo-karpati]

This pull request adds support for Socket.io's handshake authentication feature, as outlined in the Socket.io documentation. The proposed changes ensure that Elephant.io can seamlessly integrate with Socket.io servers that require authentication during the handshake phase.

Usage example:

$engine = Client::engine(
    Client::CLIENT_4X,
    $socketAddress,
    [
        'auth' => [
            "token" => 'my_secret_token',
            "user" => 'admin@example.com',
        ],
    ]
);
$this->client = new Client($engine);
$this->client->initialize();