Add documentation language switching page

[konard]

📋 Summary

This PR implements a documentation language switching page as requested in issue #33. The solution provides an interactive interface that allows users to choose between C# and Python documentation versions.

✨ Features

• Interactive Language Selection: Clean, modern UI with cards for C# and Python documentation
• URL Parameter Support: Direct linking via ?lang=csharp or ?lang=python parameters
• User Preference Storage: Remembers user's preferred language using localStorage
• Responsive Design: Mobile-friendly interface that works across all devices
• Backward Compatibility: Maintains existing documentation link structure
• Professional Styling: Matches LinksPlatform branding with modern gradients and animations

🛠 Implementation Details

The index.html page includes:

• Modern CSS with flexbox layout and responsive design
• JavaScript functionality for URL parameter handling and preference storage
• Visual indicators for user's previously selected language
• Smooth hover animations and professional styling
• Links to both /csharp/ and /python/ documentation paths

🎯 User Experience

• Users visiting the documentation root will see an attractive language selection page
• Clicking on a language card navigates to the appropriate documentation
• The system remembers the user's choice for future visits
• URL parameters allow direct linking to specific language versions
• Clean, intuitive interface that matches modern web standards

🔗 Links

• Fixes Add documentation language switching page #33
• Documentation will be available at: https://linksplatform.github.io/RegularExpressions.Transformer.CSharpToCpp

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🤖 This PR was automatically generated and implemented by the AI issue solver