Enhancement: Add Advanced JavaScript Concepts

[sharada-marasinghe]

📚 Enhancement: Add Advanced JavaScript Concepts

Description
Expand the learning content to include more advanced JavaScript topics that are commonly asked in interviews.

Proposed additions:

• Closures and Lexical Scoping
• Prototypes and Inheritance
• Async/Await and Promises
• Event Loop and Callbacks
• Modules (ES6 Import/Export)
• Destructuring and Spread Operator
• Higher Order Functions
• Generators and Iterators

Implementation details:

• Each topic should have interactive examples
• Include practice exercises
• Add to the lessons page with proper navigation
• Maintain current educational design

Priority: High
Labels: enhancement, content, education