Links to notebook files incorrectly use .md extension instead of .ipynb

[Anushkarshetty45]

Description

When using doc-builder with convert_notebooks: true, the links at the bottom of articles incorrectly point to .md files when they should be pointing to .ipynb files.

Steps to reproduce

1. Enable notebook conversion in the workflow file:

jobs:
  build:
    uses: huggingface/doc-builder/.github/workflows/build_main_documentation.yml@main
    with:
      convert_notebooks: true
      # other parameters...

2. Build documentation that contains Jupyter notebooks
3. Check the links at the bottom of the generated documentation

Current behavior

Links at the bottom of articles point to files with .md extension, for example:
[Some notebook title](notebook_name.md)

Expected behavior

Links should point to the original .ipynb files, for example:
[Some notebook title](notebook_name.ipynb)

Additional context

• This issue affects all notebook files that are converted to MDX
• The incorrect extension makes it harder for users to find and access the original notebook files
• Example repository demonstrating the issue: huggingface/cookbook (see issue Reference sections and references #181)

Environment

• doc-builder version: latest
• Using GitHub Actions workflow for documentation building