socketId added, on_connection_state_change , when pusher connected.

[usmanokara]

:sparkles: What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Feature

:arrow_heading_down: What is the current behavior?

User can listen to connection status (previous and new)

:new: What is the new behavior (if this is a feature change)?

Now user can access socket Id when connected to Pusher. This socket id is required for private and presence channel subscription.

:boom: Does this PR introduce a breaking change?

Yeah. before this user cannot subscribe to PresenceChannel. because Authentication is required. But Authentication needs socket Id. So now socket Id is available.

:bug: Recommendations for testing

User can print socket Idwhen pusher status is connected and can verify from Pusher console log.

:memo: Links to relevant issues/docs

https://github.com/ninjasolutions/flutter_pusher/issues/7 https://github.com/ninjasolutions/flutter_pusher/issues/6

:thinking: Checklist before submitting

• [x] All projects build
• [x] Follows style guide lines (code style guide)
• [x] Relevant documentation was updated
• [x] Rebased onto current develop