Add CSV to Markdown table conversion - fixes #1144 (#1176)

* 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

----

Thanks also to @benny123tw who submitted a very similar PR in #1171

packages/markitdown/src/markitdown/_markitdown.py

@@ -41,6 +41,7 @@ from .converters import (
     ZipConverter,
     EpubConverter,
     DocumentIntelligenceConverter,
+    CsvConverter,
 )
 
 from ._base_converter import DocumentConverter, DocumentConverterResult
@@ -194,6 +195,7 @@ class MarkItDown:
             self.register_converter(PdfConverter())
             self.register_converter(OutlookMsgConverter())
             self.register_converter(EpubConverter())
+            self.register_converter(CsvConverter())
 
             # Register Document Intelligence converter at the top of the stack if endpoint is provided
             docintel_endpoint = kwargs.get("docintel_endpoint")