can we make stream subscribing promise based?

[hp8wvvvgnj6asjm7]

function futuresCustomSubStream() => new Promise((rs, rj) => {

 // connect ws
 // on error -> reject
 // on success -> resolve
})

const unsubscribe = await client.ws.futuresCustomSubStream()

[hp8wvvvgnj6asjm7]

#589