settings library Null safety

Settings feature.

Classes

AdvancedSettingsControl
Widget: Go to advanced application settings (of the OS)
LanguageSwitcher
Widget: Change the application language
NotificationSwitcher
Widget: Enable or Disable push notifications
ResetAppControl
Widget: Reset the app and wipe app's data
SettingsScreen
Screen: Application settings and preferences
ThemeModeSwitcher
Widget: Switch the theme to DARK / LIGHT mode