Switch documentation theme from Material to ReadTheDocs

[wuqunfei]

Summary

This PR migrates the MkDocs documentation configuration from the Material theme to the ReadTheDocs theme, simplifying the theme setup and reducing configuration complexity.

Key Changes

• Theme Migration: Changed from material theme to readthedocs theme
• Removed Material-specific features: Eliminated Material palette configuration (light/dark mode toggle), navigation features (instant loading, tracking, sections, expand), and search enhancements
• Simplified syntax highlighting: Replaced pymdownx.highlight with codehilite extension and configured language support for Python, Rust, Bash, and JSON
• Removed Material extensions: Eliminated pymdownx.inlinehilite, pymdownx.tabbed, pymdownx.details, and Material-specific icon configurations
• Cleaned up social links: Removed GitHub social link from extra configuration
• Reorganized markdown extensions: Reordered extensions for clarity, keeping only essential ones (admonition, codehilite, toc, tables, attr_list, md_in_html, pymdownx.superfences, pymdownx.snippets)

Notable Details

• The ReadTheDocs theme provides a more lightweight, documentation-focused experience
• Language-specific syntax highlighting is now explicitly configured rather than auto-detected
• The version provider (mike) configuration is preserved for version management
• All core documentation functionality is maintained while reducing configuration overhead