reset method

Future<void> reset()

重置到默认（系统跟随 + 无自定义主题）

Implementation

Future<void> reset() async {
  _themeMode = ThemeMode.system;
  _customTheme = null;

  await SharedPreferencesBaseUtils.putString(_kThemeMode, ThemeMode.system.name);
  await SharedPreferencesBaseUtils.putString(_kCustomTheme, '');

  notifyListeners();
}