Add compatibility with iOS VOIP notifications

[nSimonFR]

This provides a way to use VOIP functionalities to the client, by sending back the iOS VOIP token and notifications payload (through deviceReady and deviceDidReceiveIncoming).
This is because this library is not compatible with libraries such as ianlin/react-native-voip-push-notification (They both implement the same methods).
This allows user to retain similar capabilities with this library (Sending VOIP notifications from their servers too, not just Twilio's).

Original commit message:

Add compatibility with iOS VOIP notifications

Send voip token to client in deviceReady callback
Use deviceDidReceiveIncoming to transfer notification payload to client

[jdegger]

Thank you for your PR and our apologies it has been quiet on this PR for so long. Please read #158 for a general update on what's happening in this repo.

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Can you explain why this PR is needed? In our tests we have VOIP Push notifications on iOS working fine without this implemented. Are we missing something?

[nSimonFR]

Hello @jdegger, thank you for your interest in my PR,

This PR - if I remember correctly, was simply some code normalization of the ios notification API in order to be on par with other librairies.
I remember using this to receive iOS VOIP push notifications (that transit through this package) and another library for standard notifications.

Seeing as this a bit of an old subject, the code may totally be outdated / requires updates with the recent changes in the ios ecosystem or your future plans for this package.

TBH I don't really trust my ios skills from two years ago and the react-native application that I am developing has dropped support for VOIP calls as this was not a feature our clients were really interested in (And difficult to maintain).

Best of luck !

[jdegger]

Thanks for the update @nSimonFR, I will be closing this PR for now, if we see that it's still needed in the future we know where to find your suggested code :)

Thanks again