feat(firebase): add clearAllNotifications method (#2867)
feat(firebase): add clearAllNotifications method (#2867)

* feat(firebase): add clearAllNotifications method

Added new method clearAllNotifications()

https://github.com/arnesson/cordova-plugin-firebase/blob/master/docs/API.md#clearAllNotifications

* remove trailing whitespace

driftyco/ionic-native,driftyco/ionic-native,driftyco/ionic-native