Feature Request: Add User Authentication for Todo Management

## Overview

It would be beneficial to implement user authentication in the MERN Todo List application. Currently, all users have access to the same todos, which could lead to privacy concerns in a multi-user environment. Adding authentication would allow users to create and manage their own personal todo lists.

## Suggested Features
- **User Registration and Login:** Implement user registration and login functionalities using JWT (JSON Web Tokens) for session management.
- **Authorization Middleware:** Protect the API endpoints so that only authenticated users can access or modify their todos.
- **User-specific Endpoints:** Modify the existing API endpoints to fetch, create, and delete todos based on the logged-in user.

## Benefit
Implementing user authentication will enhance security and improve user experience, making the app more suitable for personal use and potentially expanding its user base.

This feature would be a valuable addition to the project, allowing it to cater to individual users' needs while keeping their todos secure.