Add the participant events to the notification service RN+iOS

[graduad]

Add following events to the notification service:

• participant joined
• participant left

Only RN and iOS work. Android to be done in separate ticket.

[asadumair]

When we add a new listener how we can check or know the new user is came?? so please tell me the way because these two type of notifications are not available in react native if these are available then we can identify using these notifications
for listener participitantadded and left is not working

[graduad]

Implemented in 3.8.0 Beta 1