Add JavaScript functions documentation (functions.md)

[sindhuja-80]

📌 Description

The file JavaScript/functions.md provides a solid introduction to JavaScript functions. However, it can be improved further to make it more comprehensive, clear, and interview-oriented for beginners.

🔧 Proposed Improvements

• Add more real-world examples for better understanding
• Include a short section on function hoisting
• Improve explanations for callback and arrow functions
• Add common interview questions related to JavaScript functions
• Ensure consistent formatting and clarity across sections

🎯 Why this is important

• Helps beginners understand JavaScript functions more effectively
• Makes the documentation more useful for interview preparation
• Improves readability and learning experience
• Aligns with the repository’s goal of concept-focused documentation

📂 File Affected

• JavaScript/functions.md

🤝 Contribution

I would like to work on this issue and submit a pull request with the suggested improvements.