docs: add Simplified Chinese array methods page

[lijiayou0728]

Summary

• add the missing Simplified Chinese page for the Array Methods Plugin
• translate the prose, headings, tables, and explanatory code comments
• preserve the source page structure, API names, and executable examples

This is a focused first part of the Chinese documentation sync tracked in #1242.

User impact

Chinese readers can access the Array Methods Plugin documentation without falling back to the English page.

Validation

• git diff --check
• cd website && yarn build (English and zh-CN builds both succeeded)
• verified that the source and translation contain the same 16 code fences and 9 level-two sections

Translation note

This translation was prepared with AI assistance, compared line by line with the English source and the existing zh-CN terminology, and validated through the documentation build.

Refs #1242

[lijiayou0728]

Hi! Just a gentle follow-up on this focused zh-CN documentation PR. It adds the missing array-methods.md page, and the documentation builds passed locally. I’d be happy to address any feedback when you have a chance to review it. Thanks!

[mweststrate]

thanks!