Feature: Add "Convert to Markdown" Editor Utility Widget using markitdown (Python)

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Summary

Add an Editor Utility Widget that leverages Microsoft's markitdown Python tool to convert various file formats (PDF, Word, PowerPoint, HTML, etc.) into Markdown.

Background

Suggested by DarknessFX in #59. markitdown is a Python library published by Microsoft that supports conversion from a wide range of file formats to Markdown.

Considerations

• UI design as an Editor Utility Widget
• How to handle the Python environment dependency (integration with UE's Python plugin or external process invocation)
• Selection of supported input file formats
• Workflow to directly import conversion results as UMarkdownAsset

References

• https://github.com/microsoft/markitdown
• Suggestion: "Convert to Markdown" python tool #59