Proposal: Add Chinese (zh-CN) documentation / README translation

[zhengsuanfa]

• I have searched the issues of this repo and believe that this is not a duplicate.
  
• I have searched the documentation and believe that my question is not covered.
  

Issue

Hi, thank you for the great project!

I would like to contribute a Simplified Chinese (zh-CN) translation to help more users in China understand and use ActivityWatch.

My initial plan is:

• Add a README.zh-CN.md that is a Chinese translation of the main README.md.
• Add a short language switch section to the top of README.md, e.g.:
  • Read this in other languages: [简体中文](./README.zh-CN.md)
• Optionally, if you think it makes sense, I can also help translate some key pages of the documentation site (such as Getting started / FAQ) and follow whatever structure you prefer for multilingual docs.

Before I start working on this, I would like to confirm:

1. Are you open to having a Chinese translation in this repository?
2. Do you have any preference on:
   • The file name (e.g. README.zh-CN.md vs README_zh-CN.md)?
   • Where translations should live (root vs a docs/ or i18n/ subdirectory)?
3. Are there any existing terminology/style guidelines that I should follow when translating?

If you agree with this direction, I will:

• Fork the repository.
• Create a new branch for the zh-CN translation.
• Submit a pull request referencing this issue.

Thanks again for your time, and looking forward to your feedback!

[github-actions]

Hi there!
As you're new to this repo, please make sure you've used an appropriate issue template and searched for duplicates (it helps us focus on actual development!). We'd also like to suggest that you read our contribution guidelines and our code of conduct.
Thanks a bunch for opening your first issue! 🙏