Feature: Handling Action Buttons without Opening the App

[bbohach]

Description:
Looking for something to handle the following section in the OneSignal docs. Prevent the app from opening when clicking on an action button
https://documentation.onesignal.com/docs/action-buttons#handing-action-buttons-without-opening-the-app

Environment

1. onesignal-cordova-plugin: ^3.0.2
2. @capacitor/core: 3.4.1

[bbohach]

I was able to follow this to get it working on iOS (haven't tried Android), combined with setNotificationOpenedHandler to handle the event. But it would be nice to have a function on this plugin to make it easier to work with, so it works for both Android & iOS via this plugin