Add English translation of chapter-08.md for website.en

[Copilot]

This PR adds a complete English translation of chapter-08.md to the website.en/MarkDown/ directory, providing American English content for the international version of the programming best practices book.

Translation Overview

The translated chapter covers Practical Coding Techniques and includes:

• Think Simple Philosophy: Complexity avoidance techniques including the Giraffe-Refrigerator Principle and Saibara's Principle
• Intent Expression: Moving from How-focused to What-focused code with practical examples
• Error Handling Optimization: Defensive programming, Design by Contract, Result types, and Option types
• Performance vs Readability Balance: Optimization strategies, caching, lazy evaluation, and profiling techniques
• Quality Judgment Criteria: Code review guidelines and assessment frameworks
• Practical Exercise: Complete log analysis system implementation in C#

Technical Details

• File size: 2,256 lines (matching original 2,257 lines)
• Code examples: All preserved in original languages (C#, Java, Python, JavaScript) with translated comments
• Diagrams: Mermaid diagrams maintained with English annotations
• Images: References to ../Images/ work correctly with existing assets in website.en/Images/
• Encoding: UTF-8 without BOM
• Quality: No Japanese characters remain; complete professional translation

Content Validation

The translation maintains technical accuracy while converting all explanatory text, examples, and documentation to natural American English. All markdown formatting, code blocks, and structural elements are preserved exactly as in the original.

Fixes #183.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

Pull Request Overview

This PR adds a complete English translation of Chapter 8 ("Practical Coding Techniques") to the international version of the programming best practices book. The translation covers comprehensive coding techniques including the "Think Simple" philosophy, intent-expressing programming, error handling optimization, and performance-readability balance strategies.

• Complete translation of 2,256 lines covering practical coding methodologies
• Technical accuracy maintained with all code examples preserved in original languages
• Professional American English localization with natural language flow