mailto: and tel: links are converted to plain text #2644

_CustomMarkdownify.convert_a keeps only http, https and file links, and reduces any other scheme to the link text. Dropping javascript: links makes sense, but e-mail and phone links are common in documents and can't run code.

import io
from markitdown import MarkItDown

html = b'<p>Contact <a href="mailto:team@example.com">the team</a>.</p>'
print(repr(MarkItDown().convert_stream(io.BytesIO(html), file_extension=".html").markdown))

Actual: 'Contact the team.'

Expected: 'Contact [the team](mailto:team@example.com).'

The attached DOCX has the same link as a Word hyperlink and gives the same result. tel: links are dropped the same way.

markitdown-mailto-link.docx

Environment: markitdown 0.1.8 (main 4cc9fa1), Python 3.14.8, Ubuntu 24.04.5 LTS.