feat: Add an optional Windows 11 Fluent GUI desktop extension

[omererman]

🚀 Purpose of this Pull Request

Hello MarkItDown Maintainers!

I have built a modern, standalone Windows 11 Fluent Design GUI desktop application for the MarkItDown library. Since MarkItDown is a Microsoft project, I wanted to provide a native-looking, user-friendly desktop experience for non-CLI users who want to convert their documents seamlessly.

To respect the core architecture of this project, all GUI-related code lives entirely inside an isolated gui/ directory and does not alter or interfere with the core library or CLI source code.

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✨ Key Features of the GUI Extension

• Windows 11 Fluent UI: Designed using PyQt6 and qfluentwidgets to match the native Windows 11 aesthetic (rounded corners, smooth animations, Segoe UI fonts, dark/light mode sync).
• Multilingual Support: Supports 6 major languages out of the box (English, Turkish, Spanish, French, German, and Chinese) with automatic system language detection and a dynamic UI language switcher.
• Asynchronous Processing: Built using QThread to prevent UI freezing/crashing during heavy document (PDF/Office) conversions.
• Dynamic File Recognition: Visual drop-zone card that dynamically changes its document icon colors based on the file type dropped (e.g., Red for PDF, Blue for Word, Green for Excel).
• Drag and Drop Support: Users can instantly drop files into the app to convert them.

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🛠️ How it is Structured

markitdown/
│── src/                  # Untouched Core Library
│── packages/             # Untouched Packages
└── gui/                  # New isolated GUI extension
    ├── markitdown_gui.py # Main GUI Code
    └── requirements.txt  # Dependencies for the GUI


I understand if a desktop GUI might be considered out of the strict scope for the core library repository. However, I believe this could serve as an excellent official/experimental extension or a template for community tools.

I am completely open to your feedback, suggestions, or moving this under a contrib/ or examples/ directory if preferred. Thank you for this amazing library!

[omererman]

@microsoft-github-policy-service agree