Add README.ru-RU.md and CONTRIBUTING.ru-RU.md following the existing
localization pattern (zh-CN, ja-JP, ko-KR), and add the Русский link to
the language switcher line in all README and CONTRIBUTING variants.
Also add the previously missing 한국어 link to the CONTRIBUTING.zh-CN.md
and CONTRIBUTING.ja-JP.md switchers.
Closes#100
* docs: add GitHub issue and PR templates
Add structured issue templates for bug reports, feature requests, and docs reports with YAML forms. Include a pull request template with checklist for contribution quality.
* docs: add bilingual contributing guide (EN & zh-CN)
Provide detailed contribution guidelines covering development setup, coding standards, commit conventions, PR workflow, and community conduct in both English and Chinese.