Reducer.swift

 func todoReducer(state: [String], action: Action) -> [String] {
	 var newState = state
	 switch action {
	 case .addTodoItem(let text):
		 newState.append(text)
	 case .removeTodoItem(let index):
		 newState.remove(at: index)
	 }
	 return newState
 }