In a flutter app running on an iOS device, using the firebase_messaging package, when receiving a push notification via APNS that has a localized key, i.e. the alert part of the payload contains something like
"loc-key" : "GAME_PLAY_REQUEST_FORMAT",
the push notification will only display the key GAME_PLAY_REQUEST_FORMAT unless you do something to localize it on the device (cf. https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/generating_a_remote_notification or https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CreatingtheNotificationPayload.html). The standard way for this seems to be to add the key to the Localizable.strings. So the question presents itself:
How do you add Localizable.strings to an existing Flutter project?