Add automated translation tools - Addresses #1494

Provides automated translation tools to translate JavaGuide documentation
to multiple languages, addressing the 5-year-old request in issue #1494.

Features:
- Python and Java implementations (876 lines total)
- Supports 20 languages including English, Spanish, French, etc.
- Batch translates all markdown files in docs/ folder + README.md
- Preserves directory structure (docs/ -> docs_en/)
- File naming: file.md -> file.en.md
- Progress tracking with JSON (.translation_progress.json)
- Skips already translated files
- Rate limiting to avoid API throttling
- Free Google Translate API (no key required)
- Handles large files with smart chunking (4000 chars)
- Preserves markdown formatting and code blocks

Files added:
- translate_repo.py (318 lines) - Python implementation
- TranslateRepo.java (386 lines) - Java implementation
- TRANSLATION_TOOLS.md (172 lines) - Comprehensive documentation

Usage:
  Python: python3 translate_repo.py
  Java: javac -cp gson.jar TranslateRepo.java && java -cp .:gson.jar TranslateRepo

Output structure:
  docs/ -> docs_en/ (for English)
  README.md -> README.en.md

Performance:
  ~1 file per 5-10 seconds
  JavaGuide (292 files) ≈ 2-3 hours

This enables the community to easily create translations for any of the
20 supported languages, making JavaGuide accessible to developers worldwide.

Addresses #1494