add method
add item to cache; expired: hours
defaults to 0
Implementation
static Future<bool> add(String key, String value, {int expired = 0}) async {
MmkvFlutter mmkv = await MmkvFlutter.getInstance();
final timespan =
DateTime.now().add(new Duration(hours: expired)).millisecondsSinceEpoch;
/// add timespan to value so we can use it later.
final v = '$timespan:$value';
return mmkv.setString(_getPrefix(key), v);
}