Sync and update Simplified Chinese translation (README_zh.md)

[AutomaticOrca]

Hi maintainers,

I noticed that the Simplified Chinese translation is outdated and diverges from the main English README. I’ve synced the content with the latest English version, fixed some minor issues, and propose unifying the translation file under README_zh.md (without the ??? one 😅). Some of the wording sounded a bit informal, so I’ve polished the phrasing and double-checked for accuracy.

I’ll submit a pull request shortly. As a gopher born in China coding in AU, I appreciate for maintaining this awesome project.

Regards,
JY