Setting for notifications when app in foreground

[FallenRiteMonk]

Is your feature request related to a problem? Please describe.

On iOS push notifications are shown even when the app is in foreground, while on Android they are not. These different default behaviors make it impossible to create the same look and feel for iOS and Android.

Describe the solution you'd like

There exists a issue (possible even more than one) in ernesson plugin with multiple PRs to solve the problem:

• Hide iOS push notifications when app is in foreground arnesson/cordova-plugin-firebase#835

• Hide foreground notification with --variable on iOS arnesson/cordova-plugin-firebase#913

• Added API method enableForegroundNotifications() arnesson/cordova-plugin-firebase#1056

[shastox]

I suggest making this setting.