Function whatsappweb::connection::new

pub fn new<Q: Fn(QrCode) + Send + 'static, H: WhatsappWebHandler<H> + Send + Sync + 'static>(
    qr_cb: Q, 
    handler: H
) -> (WhatsappWebConnection<H>, JoinHandle<()>)

Create new connection and session. Will eventual call qr_cb with the generated qr-code.