Insert ui state as resource and system to react to changes

[JunichiSugiura]

Criteria

• insert each ui state as individual resource
• automatically trigger rerender when ui state resources are changed

Old

fn update_todo_list(
    mut events: EventReader<NewTodoList>,
    mut ui_state: EventWriter<UiState>,
) {
    for e in events.iter() {
        ui_state.send(UiState::TodoList(e.todo_list.clone()));
    }
}

New

fn update_todo_list(
    mut events: EventReader<NewTodoList>,
    mut todo_list: ResMut<TodoList>,
) {
    for e in events.iter() {
        *todo_list = e.todo_list.clone();
    }
}

// generated
fn dispatch_todo_list(
    todo_list: Res<Vec<UiTodo>>,
    mut ui_state: EventWriter<UiState>,
) {
    if todo_list.is_changed() {
        ui_state.send(UiState::TodoList(todo_list.clone()));
    }
}