Feature/showing connecting status on answering a call

[aarkalyk]

With introducing this PR, on answering a call user will see connecting status and updateConnectionStatus method will need to be called to indicate either start or failure of a call.
This will only work if showConnectionState argument is passed to displayIncomingCall, otherwise a call will just get connected immediately as it does in the current version.

Solves the issue #22

[ckrodrigues]

@ianlin this seems really useful, can you take a look at it?

[zxcpoiu]

@aarkalyk

Hi, Does this introduce a breaking change?
Said, what would happen if a user use the older version and does not call updateConnectionStatus ?

[aarkalyk]

@zxcpoiu Just introduced some changes. There shouldn't be any breaking changes now.
@ianlin Can you take a look please?

[zek]

@aarkalyk I tried your PR. It works as below but If I updateConnectionState after connection is established no one can hear each other. Do you have any solutions for this problem?

      NativeModules.RNCallKeep.updateConnectionState(true);
      if (data.callUUID) {
        this.callManager.getSession(data.callUUID).acceptCall();
      } else {
        this.callManager.incomingSession.acceptCall();
      }