[Feature]: Consider supporting CJK Friendly emphasis extension (`remark-cjk-friendly`) instead of plain CommonMark/GFM emphasis

[tats-u]

What problem does this feature solve?

#2644

The plain CommonMark/GFM has a specification defect that bold/emphasis frequently fail in Chinese (or Japanese) text.

**中文文本（带括号）。**这句子继续也没问题。

• Expected: 中文文本（带括号）。这句子继续也没问题。
• Actual: **中文文本（带括号）。**这句子继续也没问题。

There are some Remark plugins to suppress this problem as a worksaround (demo), but you have to disable mdxRs first, messing up one of the biggest advantages of Rspress:

import remarkCjkFriendly from "remark-cjk-friendly";
import remarkGfmStrikethroughCjkFriendly from "remark-cjk-friendly-gfm-strikethrough";
import { defineConfig } from "rspress/config";

export default defineConfig({
  markdown: {
    mdxRs: false, // IMPORTANT! This is mandatory for Rspress!
    // Once you turn off `mdxRs`, you can add `remarkPlugins` and `rehypePlugins` like other remark-based site generators.
    remarkPlugins: [remarkCjkFriendly, remarkGfmStrikethroughCjkFriendly],
  },
});

VitePress is going to bundle the markdown-it variant of these plugins and enable it by default since 2.x (still beta now).

What does the proposed API look like?

If opt-out like VitePress:

import { defineConfig } from "rspress/config";

export default defineConfig({
  markdown: {
    cjkFriendlyEmphasis: false, // If you want to disable it for some reson
  },
});

The most difficult point is that we have to fork and modify the markdown(-rs) crate first because it will not support extensions other than the most popular ones. The comrak crate has implemented this extension so we can reuse its implementation as a Rust-based model implementation.
This extension is compatible with the plain CommonMark/GFM except for emphasis/strikethrough handling for CJK characters.

[SoonIter]

nice suggestion!