Support CJK Friendly Emphasis

[tats-u]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Motivation

• vuejs/vitepress@9fc8462
• [Feature]: Consider supporting CJK Friendly emphasis extension (remark-cjk-friendly) instead of plain CommonMark/GFM emphasis web-infra-dev/rspress#2772
• https://xoofx.github.io/markdig/docs/extensions/cjk-friendly-emphasis/
• https://github.com/web-infra-dev/rspress/releases/tag/v2.0.5
• https://streamdown.ai/docs/plugins/cjk
• docs: Suggest remark-cjk-friendly in migration guide #10892

We have to insert extra spaces for workaround:

Docusaurus 3 has a regression that asterisks */** around punctuation including ` representing inline codes and [/] representing links are not recognized as emphasis. This affects especially on Chinese and Japanese documents.

https://docusaurus.io/docs/next/migration/v3#other-markdown-incompatibilities suggests using remark-cjk-friendly (#10892) but it should be opt-in or opt-out in the future.

There are two proposed methods for setting it up:

import type { Config } from "@docusaurus/types";
import type { Options } from "@docusaurus/preset-classic";
const config: Config = {
  // *snip*
  markdown: {
    cjkFriendlyEmphasis: true, // Plan (1)
  },
  presets: [
    [
      "classic": 
      {
        cjkFriendlyEmphasis: true, // Plan (2),
        // *snip*
      } as Options
    ],
  ],
  // *snip*
};

export default config;

Also there are 3 proposed strategies for enabling it:

• opt-out & dependencies
• opt-in & dependencies
• opt-in & optional peerDependencies (users need to run pnpm add remark-cjk-friendly remark-cjk-friendly-strikethrough)

Self-service

• I'd be willing to do some initial work on this proposal myself.

[tats-u]

You can add the prefix experimental_ if needed.

[tats-u]

We have to designate remarkPlugins multiple times without the official support:

https://github.com/tats-u/markdown-cjk-friendly/blob/75a7ebd1341b0e1beff2be5bf8830a0b514fc34d/demos/docusaurus/docusaurus.config.js#L8-L81