[docs](Node): Updated Node theory concept

[RakshaBKottari]

📑 Description

I have covered the following topics

1. What is Node.js?
2. Features of Node.js
3. Use Cases for Node.js
4. Comparison with Other Technologies (e.g., Python, PHP)
5. Installing Node.js
6. Setting Up a Development Environment
7. Using Node Version Manager (NVM)
8. Basic Command Line Usage
9. Creating Your First Node.js Application
10. Understanding the Event Loop
11. Callbacks, Promises, and Async/Await
12. Modules and the Module System
13. CommonJS vs. ES Modules
14. Built-in Modules (e.g., File System, HTTP, Events)

✅ Checklist

• [X] I have made corresponding changes that follow the style of this project.

🔗 Related Issue(s)

Fixes #21

🚀 Types of changes

• [x] Documentation update (docs for this project)

📸 Screenshots (if applicable)

💬 Additional Comments (if applicable)