docs: add document for lidarseg directory

[ktro2828]

What

This pull request updates the dataset documentation to clarify the directory structure and add information about optional LiDAR segmentation annotations. The changes improve clarity and provide guidance for datasets that include LiDAR segmentation in the nuScenes format.

Documentation improvements:

• Updated the dataset directory structure in docs/schema/index.md to indicate that annotation, data, input_bag, and map are directories, and added an optional lidarseg/ directory for LiDAR segmentation annotations.
• Added a new section describing the LiDAR segmentation annotation format, specifying its compatibility with the nuScenes format and detailing the contents of the lidarseg/annotation/ directory.

Configuration update:

• Added an extra section to the options in mkdocs.yaml for documentation generation, which may be used for further configuration.

[Copilot]

Pull request overview

This pull request enhances the dataset documentation by adding clarity to the directory structure and introducing information about optional LiDAR segmentation annotations. The changes make it explicit which items are directories and document support for LiDAR segmentation data in the nuScenes format.

Key changes:

• Clarified directory structure notation by adding trailing slashes to distinguish directories from files
• Added documentation for the optional lidarseg/ directory and its annotation format
• Updated mkdocs.yaml configuration with an extra section for documentation generation options

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
mkdocs.yaml	Added extra section to mkdocstrings plugin options for future configuration
docs/schema/index.md	Updated directory structure notation and added LiDAR segmentation annotation documentation

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.