Update docs

[yu-ta-sato]

Description

This pull request updates documentation and configuration for the City2Graph project to improve clarity, searchability, and branding for 2026. The main changes include enhanced descriptions and keywords for SEO, refined example titles and content, updated copyright years, and improved navigation and plugin support.

Documentation and SEO improvements:

• Added detailed descriptions and comprehensive keywords to docs/api/index.md and docs/examples/index.md for better discoverability and clarity. [1] [2]
• Refined example titles and descriptions in docs/examples/index.md to emphasize use cases and technologies (e.g., Heterogeneous GNNs, OSM, GTFS, OD Matrices).

Branding and copyright updates:

• Updated copyright year to 2026 in LICENSE and mkdocs.yml to reflect ongoing development. [1] [2]

Navigation and configuration enhancements:

• Improved example navigation titles in mkdocs.yml for clarity and consistency, aligning with updated example descriptions.
• Added the mike plugin to mkdocs.yml to support versioned documentation.

Related Issues

NA

Checklist

• I have read the Contributing Guide.
• I have updated the documentation, if necessary.
• I have added tests to cover my changes.
• All new and existing tests passed.
• Pre-commit checks passed locally.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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