Add a playback_ready field to the "/" api response

[dubeyKartikay]

While trying to test the /player/play endpoint. I ran into a bug where the app would say that "its up" ( GET "/" and "/status" would return 200) but when i hit the /player/play endpoint, the playback would fail.

sometimes the connection id was not set, sometimes the volume sync hadn't happened, which led to the volume of the track changing mid playback.

So i had to expose a playback_ready field that is set to true whenever its safe to call /player/play and false otherwise

[guidcruncher]

could this be emitted as a event toi?

[dubeyKartikay]

Actually that's a great idea, I'll make the changes

[dubeyKartikay]

Actually, after adding this, and testing for a bit.
i found out that emmiting this as an event is... finiky and not all that reliable.
Here's why :

1. You probably just started go-librespot, that's why you need to know when its ready for playback
2. To revieve the playback_ready event, you have to connect to the websocket before the event gets emmited. Otherwise youll miss it.

This kinda makes things unreliable.

@devgianlu what are your thoughts on this?

[devgianlu]

With the suggested changes the PR should be smaller.

The WS event can stay, it doesn't hurt and can still be useful if the initial connect state PUT takes a while. You can always check via the API and then wait for the event to avoid polling.