* feat: Add CSV to Markdown table converter
- Add new CsvConverter class to convert CSV files to Markdown tables\n- Support text/csv and application/csv MIME types\n- Preserve table structure with headers and data rows\n- Handle edge cases like empty cells and mismatched columns\n- Fix Azure Document Intelligence dependency handling\n- Register CsvConverter in MarkItDown class
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Thanks also to @benny123tw who submitted a very similar PR in #1171