saveString method
Method for storing a String with a defined key.
Example:
// RCache.common.saveString("data string", key: RCacheKey("string"));
Implementation
@override
Future<void> saveString(String string, {required RCacheKey key}) async {
  try {
    return await methodChannel.invokeMethod(
      RCacheMethod.key.save.string,
      rArgs(type: RCacheMethod.key.common, key: key, value: string),
    );
  } on PlatformException catch (e) {
    return Future.error(e);
  }
}