Add push notification methods & update delegate re foreground notification (iOS only)

[rvencio880]

This will implement the following changes:

1. Add an iOS only method -- hasUserAnsweredNotificationPrompt -- that gets a boolean indicating if the user received and answered (allowing or not) the prompt to allow notifications
2. Add an iOS only method -- registerPushNotification -- for prompting for permission to send push notification if the user was never prompted with it
3. Update delegate method -- userNotificationCenter:didReceiveNotificationResponse:withCompletionHandler -- to clear the 'applicationIconBadgeNumber' once user notification was sent from Braze. This ensures that foreground notifications are being delivered

[santiq]

@radixdev @Bucimis @briancaw @hokstuff

[Bucimis]

Hi @rvencio880, thanks for this contribution. Updating our iOS + Cordova push integration for the future is part of our 2022 roadmap and will be built on top of our upcoming Swift SDK. We plan to significantly upgrade automation, customization, and flexibility in the new world.

Let us know if you'll be able to use this fork for your needs until then.