update method
Implementation
Future<void> update(String activityId, Map<String, dynamic> contentState) async {
if (_platform() == 'ios') {
await NexusPlatform.instance.liveActivityUpdate(activityId: activityId, contentState: contentState);
} else if (_platform() == 'android') {
await renderNexusLiveActivity({'event': 'update', 'activityId': activityId, 'contentState': contentState});
}
}