Add English translation of appendix-f.md to website.en

[Copilot]

This PR adds a complete English translation of appendix-f.md to the website.en/MarkDown/ directory. The original Japanese file contained a comprehensive self-assessment tool for programming skills in the AI era.

What was translated

The appendix-f.md file is a 360-line comprehensive programming skill assessment tool that includes:

• Seven Principles of Beautiful Code assessment across three skill levels (Recognition, Application, Leadership)
• AI era adaptation diagnosis covering basic utilization, collaboration, and strategic levels
• Practical application skills diagnosis for individual, team, and organizational levels
• Overall evaluation and career path guidance with scoring system (135 points total)
• Personal growth plan template with 3-month, 6-month, and 1-year goals
• Learning resources by field for continued skill development

Translation approach

• Complete American English translation with no remaining Japanese text
• Preserved exact markdown structure including all checkboxes, tables, and formatting
• Maintained technical accuracy for programming terminology and concepts
• Updated image references to point to ../Images/banner-appendix-f.svg (verified accessible)
• UTF-8 encoding without BOM as specified in requirements

Validation performed

• Confirmed no Japanese characters remain using regex validation
• Verified line count matches original (360 lines)
• Tested website.en functionality with local HTTP server
• Confirmed image references work correctly
• Validated markdown structure is preserved

The translated file provides English-speaking developers with the same comprehensive self-assessment capabilities as the Japanese version, supporting the international accessibility of this programming best practices resource.

Fixes #206.

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[Copilot]

Pull Request Overview

This PR adds a comprehensive English translation of the programming skills self-assessment tool (appendix-f.md) to the English version of the website. The translation maintains the complete structure and functionality of the original Japanese assessment while making it accessible to English-speaking developers.

Key changes:

• Complete English translation of 360-line comprehensive programming assessment tool
• Preserved markdown structure including checkboxes, tables, and formatting
• Updated image reference to correct English website path