Wrong condition to create wss url in web_socket_transport.dart

[ddcanh]

Hi guys, thanks for the lib. It works great on flutter web.
However, I think there is a bug in web_socket_transport.dart.
In line 32 you add access token to url by this condition:
url += (url.contains('?') ? '?' : '&') + "access_token=$encodedToken";
I need to fix this line to get it work:
url += (url.contains('?') ? '&' : '?') + "access_token=$encodedToken";
Please check!