feat: add educational OOP concepts following TypeScript Handbook (#290)

[MOHD-TAHA-KHAN]

[FEATURE]: OOP Educational Guide - Abstraction, Inheritance, Encapsulation, and Polymorphism

📝 Description

This PR resolves #290 by introducing a structured set of educational examples focused on Object-Oriented Programming (OOP) in TypeScript. Following the guidelines from the TypeScript Handbook, these examples are designed to help contributors and students understand how to architect clean, reusable, and maintainable code.

🚀 Key Educational Concepts

To provide a clear learning path, the code is organized into concept-specific files:

• oop/Abstraction.ts: Demonstrates the use of abstract classes and methods to define blueprints.
• oop/Inheritance.ts: Shows how to extend classes using the extends and super keywords.
• oop/Encapsulation.ts: Illustrates data protection using private and protected access modifiers along with getters.
• oop/Polymorphism.ts: Provides examples of using interfaces to treat different concrete implementations as a single type.

📚 Documentation References

Each file is heavily commented and refers to the following official documentation for deeper understanding:

• TypeScript Handbook: Classes
• TypeScript Handbook: Member Visibility
• TypeScript Handbook: Abstract Classes

🧪 Testing

Comprehensive unit tests have been added in oop/__tests__/OOP.test.ts to verify the mathematical and logical correctness of the examples.

• Verified Inheritance and Abstraction logic via Rectangle area calculation.
• Verified Encapsulation by testing private property protection in BankAccount.
• Verified Polymorphic behavior using different Logger implementations.

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By structuring these as separate files, this contribution serves as a living syllabus for the repository's OOP standards.