Send commands based on transport state instead of connected state

[ThisIsEsh]

Change sending commands logic, rely on transport state instead of client connected state,

Fixes missing subscribe frames bug for unsubscribes, that have been called between transport open and connected frame response for server.

Also it will allow to send subscribe requests after transport has been opened without waiting for response from server.

Notes:

Removed optimistic flag from Subscription, it does not make sense, because we can just rely on transport state.

Removed skipSending flag from Subscription, it's not longer required, because it have been used only for sending optimistic subs in emulation transport and this optimistic subs are removed right now, because they would require implementation of queue of unsubscribe frames, which would lead to way more complicated logic. But it will be easy to return, if will be required later.

Also I have made a public method in centrifuge, that indicates that transport is ready, so it can be used inside subscription without @ts-ignore, but I think it would be good idea to move all logic of skipping commands sending into Centrifuge client and remove early returns from Subscription.

P.S. I have spent some time trying to properly configure centrifugo server instance to be able to run all tests locally, what do you think about adding docker-compose file + config.json to this repo?

[FZambia]

Many thanks @ThisIsEsh

Will take a look today and during the weekend.

Regarding local tests, there is a single command used in CI:

centrifuge-js/.github/workflows/ci.yml

Line 21 in e8d553b

run: docker run -d -p 8000:8000 -e CENTRIFUGO_PRESENCE=true centrifugo/centrifugo:latest centrifugo --client_insecure --http_stream --sse

But adding docker-compose makes sense anyway - let's solve separately - #279

[FZambia]

This looks great, efficient and simplifies implementation a lot. Found a couple of things to fix. Could you please check it out, and I'll make one more iteration after that.

[FZambia]

This is 💎, many thanks @ThisIsEsh