feat: Add Korean translation for README with bilingual navigation

[hanaoverride]

📝 Summary

Added Korean translation for the main README.md file and implemented bilingual navigation menu for better accessibility.

🌟 Changes Made

• ✅ Korean Translation: Complete translation of readme.md to readme_ko.md in /translation/ko/ directory
• ✅ Language Menu: Added language selection menu to both English and Korean versions
• ✅ Technical Terms: Preserved English technical terms alongside Korean translations for better searchability
• ✅ Beginner-Friendly: Added concept explanations for each section to help beginners understand complex topics

🎯 Translation Features

• English Term Preservation: Technical terms include both Korean and English (e.g., "매개변수 효율적 미세 조정 (Parameter-Efficient Fine-Tuning, PEFT)")
• Concept Explanations: Added detailed explanations for each technical concept. This will help beginners understand the meaning of terminologies related to LLMs.
• Consistent Terminology: Maintained consistent translation throughout the document

🔗 Navigation

Users can now easily switch between languages using the language selection menu at the top of each document.