docs: add Chinese translation and support multi-language structure

[hzhangxyz]

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[Copilot]

Pull request overview

This PR adds Chinese translation support and restructures the documentation to support multiple languages. The root index.md is converted to a language router that detects the user's browser language and redirects to either the English (/en/) or Chinese (/zh/) documentation. The VitePress configuration is updated with locale-specific navigation and sidebars for both languages.

Key Changes

• Implemented automatic language detection and routing at the documentation root
• Reorganized all English documentation under /en/ subdirectory
• Updated VitePress configuration with multi-language locale support including separate navigation and sidebar configurations for English and Chinese
• Fixed the Sudoku Vue component import path to work with the new structure

Reviewed changes

Copilot reviewed 4 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/index.md	Converted from static homepage to Vue-based language router that detects user language and redirects appropriately
docs/en/index.md	English homepage moved to /en/ subdirectory with original content
docs/en/getting-started/installation.md	Installation guide moved to English locale directory
docs/en/getting-started/quickstart.md	Quick start guide moved to English locale directory
docs/en/concepts/terms.md	Terms concept documentation moved to English locale directory
docs/en/concepts/search.md	Search engine concept documentation moved to English locale directory
docs/en/concepts/rules.md	Rules concept documentation moved to English locale directory
docs/en/api/typescript.md	TypeScript API reference moved to English locale directory
docs/en/api/python.md	Python API reference moved to English locale directory
docs/en/api/cpp.md	C++ API reference moved to English locale directory
docs/en/support-packages/bnf.md	BNF package documentation moved to English locale directory
docs/en/support-packages/egg.md	E-Graph package documentation moved to English locale directory
docs/en/examples/basic.md	Basic examples moved to English locale directory
docs/en/examples/sudoku.md	Sudoku example moved to English locale with corrected Vue component import path
.vitepress/config.mts	Updated configuration to support locales with separate English and Chinese navigation/sidebar structures

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