* *BREAKING CHANGES*
    * `onNotificationOpen()` renamed to `onMessageReceived()`
    * Changed key names for custom notification properties in FCM data messages to display system notifications in foreground.
    * Message payload is always delivered to `onMessageReceived()` for both data and notification messages.
    * `messageType` key indicates type of FCM message: `notification` or `data`
    * `tap` is only set when `messageType` is `notification`
    * Explicit dependency on `cordova-plugin-androidx-adapter` since Android implementation uses AndroidX so is incompatible with Android Support Library.
    * Set `remote-notification` background mode in native Xcode project for iOS.
    * Reworked plugin documentation.
* Support customisable display of system notifications while app is in foreground for both notification and data messages (both Android & iOS).
* Set default color accent and notification channel for FCM notifications.
* Add support for default and custom notification ...