Proposal: Add a community showcase or related projects section

Hi MarkItDown team,

First of all, thank you for building and maintaining MarkItDown. It is a very useful project for converting documents and other files into Markdown.

I recently built a small web-based tool based on MarkItDown:

https://doc2md.cn

It provides a simple UI for uploading supported files, converting them to Markdown, previewing the result, copying the Markdown, and downloading it as a .md file.

I was wondering whether the MarkItDown repository would be open to adding a small "Community Projects", "Related Projects", or "Built with MarkItDown" section in the README. This could help users discover practical tools built on top of MarkItDown, and also make it easier for community projects to link back to the official repository.

If this sounds acceptable, I would be happy to submit a PR adding such a section and include my project as one example.

Thanks again for the great work.

Start by reviewing the repository README and the discussion on this issue. If accepted, add a clearly labeled community or related-projects section with the proposed doc2md.cn example, then confirm that the README renders correctly and the project link is accurate.