Utility function to wait a websocket to return transaction information

[melanke]

@hal0x2328 made a websocket service on Dora that is very useful: It simply send a single message with transaction information right when it gots it and then it closes the websocket connection.

This is very useful because after a invokefunction is important to be sure if the transaction was successful and which information was sent via notification by the smart contract, so, you could do something like this:

const resp = await walletConnectCtx.invokeFunction(scripthash, method, params)
const transaction = await dora.waitForTransaction(resp.result) // new method to open, listen and close a websocket
const notifications = transaction.filterNotifications(scripthash, eventname) // new method to make it easier to get a notification

I believe the endpoint of the Websocket is:
wss://dora.coz.io/ws/v1/neo3/testnet/log/<transaction_id>

I would be happy to implement this issue, but probably there is a lot of decisions to be made regarding the responses of those methods