Add Chinese (Simplified) translation for documentation

[clanzhang]

Summary

I'd like to contribute a Simplified Chinese (zh-CN) translation of the RocketSim documentation site.

Proposal

Starlight supports internationalization out of the box. The plan:

1. Add locales config in astro.config.ts with en (default) and zh-CN
2. Create translated content under src/content/docs/zh-cn/ mirroring the English structure
3. Add zh-CN UI labels via Starlight's locales config

Scope

• Start with the most user-facing pages first (Getting Started, CLI, App Actions, etc.)
• Code examples and CLI commands stay in English (only translate prose)
• Translate page titles, descriptions, and sidebar labels

Notes

• This won't affect the main RocketSim app or CLI — documentation site only
• I can maintain the translations over time as content updates

Would this be welcome? Happy to start with a subset of pages as a proof of concept.

[AvdLee]

100%, we would love that! This is also exactly why we run our docs open source. Feel free to go ahead and open a PR!