Subscription Event Engine and Events Listener implementation

[parfeon]

feat(event-engine): add general event engine

Add core Event Engine implementation with the required set of types and methods.

feat(subscribe-event-engine): add subscribe event engine

Add Subscribe Event Engine built atop of the core Event Engine implementation.

feat(entities): add base PubNub entities

Add the following entities: channel, channel group, uuid and channel metadata objects.

feat(subscription): add subscription and subscription sets

Add objects to manage subscriptions and provides interface for update listeners.

feat(listeners): add event listener

Add new event listeners, which make it possible to add listeners to a specific entity or group of entities (though subscription and subscription set).

[Xavrax]

10k changes

[parfeon]

@pubnub-release-bot release

[pubnub-release-bot]

🚀 Release successfully completed 🚀