add a code sample to include app init/splash screen

[csells]

e.g.

// unnamed routes
redirect: (state) {
  // capture deep link
  final from = state.queryParams['from'] ?? state.subloc;

  // check for the app to be ready
  final initialized = appState.initialized;
  final initializing = state.subloc == '/init';
  if (!initialized && !initializing) return '/init?from=$from';

  // check for the user to be logged in
  final loggedIn = loginInfo.loggedIn;
  final loggingIn = state.subloc == '/login';
  if (!loggedIn && !loggingIn) return '/login?from=$from';
  if (loggedIn && loggingIn) return '/';

  // strip the deep link
  if( state.queryParams.contains('from') ) return state.subloc;

  // no redirect
  return null;
}

// named routes
redirect: (state) {
  // capture deep link
  final from = state.queryParams['from'] ?? state.subloc;

  // check for the app to be ready
  final initialized = appState.initialized;
  final initializing = state.subloc == state.namedLocation('init');

  if (!initialized && !initializing) {
    return state.namedLocation('init', queryParams: {'from': from);
  }

  // check for the user to be logged in
  final loggedIn = loginInfo.loggedIn;
  final loggingIn = state.subloc == state.namedLocation('login');

  if (!loggedIn && !loggingIn) {
    return state.namedLocation('login', queryParams: {'from': from});
  }

  if (loggedIn && loggingIn) return state.namedLocation('home');

  // strip the deep link
  if( state.queryParams.contains('from') ) return state.subloc;

  // no redirect
  return null;
}

[csells]

fixed in the loading page example: https://github.com/csells/go_router/blob/main/go_router/example/lib/loading_page.dart#L81