Add bilingual README with developer contribution guidance

[Copilot]

Adds guidance for developers maintaining this legacy adapter module and splits documentation into English/Chinese versions.

Changes

Developer Notes section

• Warns that future Nacos versions may not support this module
• Documents prerequisite: clone and locally compile alibaba/nacos per official build guide
• Explains rationale: required Nacos dependencies aren't published to Maven Central

Bilingual documentation

• README.md → English
• README_CN.md → Chinese (简体中文)
• Cross-linked with language switcher at top of each file

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[lingma-agents]

无法获取合并请求的变更信息，代码审查流程终止。