feat: add summary for easier usage

[peter-jerry-ye]

Add summary for each section. User may choose to download them for prompting LLMs.

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

Here are three potential issues or observations from the provided git diff output:

1. Python Version in .readthedocs.yaml:

   • The Python version specified in .readthedocs.yaml is "3.13". As of now, Python 3.13 is not a released version. This could cause issues during the build process if the specified version is not available. Consider using a stable and released version of Python, such as "3.11" or "3.12".

2. No Newline at End of File:

   • Several files, such as next/llm.py, next/.gitignore, and next/tutorial/index.md, are missing a newline at the end of the file. While this is not a critical issue, it is a good practice to ensure that all files end with a newline character to avoid potential issues with certain tools and text editors.

3. Hardcoded Paths in llm.py:

   • The llm.py script contains hardcoded paths like BUILD_DIR="_build/markdown" and output_file = f"download/{directory}/summary.md". This could lead to issues if the script is run in a different environment or if the directory structure changes. Consider making these paths configurable or relative to the script's location to improve flexibility and maintainability.

These are the most notable observations from the diff. Addressing these issues could improve the robustness and maintainability of the codebase.