i18n(zh-cn): Translate `Endpoints.md`

[mogeko]

What kind of changes does this PR include?

• New or updated content
• Translated content
• Changes to the docs site code

Description

Translated Endpoints document. Its English reference comes from here.

At the same time, we modified a code error for /en/core-concepts/endpoints.md:

https://github.com/withastro/docs/blob/6d387a144de27ee78b75a740623489907f174163/src/pages/en/core-concepts/endpoints.md?plain=1#L32-L38

export async function get({ params, request }) { 
   const response = await fetch("https://astro.build/assets/press/full-logo-light.png"); 
   const buffer = Buffer.from(await response.arrayBuffer()); 
   return { 
     body: buffer, 
     encoding: 'binary', 
   };
}

He was marked as missing in #438.

Please labeled this PR with hacktoberfest-accepted. :kissing_heart:

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