feat: add markdown-it-cjk-friendly

closes #3762
closes #4752

BREAKING CHANGE: [markdown-it-cjk-friendly](https://www.npmjs.com/package/markdown-it-cjk-friendly) is enabled by default. This intentionally deviates from the official commonmark spec for the benefit of CJK users. **For most users, no change is required.** If you were using hacks to patch `scanDelims`, you can remove those. To disable the plugin, set `markdown: { cjkFriendly: false }` in your vitepress config.

package.json

@@ -158,6 +158,7 @@
     "markdown-it-anchor": "^9.2.0",
     "markdown-it-async": "^2.2.0",
     "markdown-it-attrs": "^4.3.1",
+    "markdown-it-cjk-friendly": "^1.2.0",
     "markdown-it-container": "^4.0.0",
     "markdown-it-emoji": "^3.0.0",
     "markdown-it-mathjax3": "^4.3.2",

src/node/markdown/markdown.ts

@@ -22,6 +22,7 @@ import type {
 import anchorPlugin from 'markdown-it-anchor'
 import { MarkdownItAsync, type Options } from 'markdown-it-async'
 import attrsPlugin from 'markdown-it-attrs'
+import mditCjkFriendly from 'markdown-it-cjk-friendly'
 import { full as emojiPlugin } from 'markdown-it-emoji'
 import type { BuiltinLanguage, BuiltinTheme, Highlighter } from 'shiki'
 import type { Logger } from 'vite'
@@ -188,6 +189,13 @@ export interface MarkdownOptions extends Options {
    * @see https://vitepress.dev/guide/markdown#github-flavored-alerts
    */
   gfmAlerts?: boolean
+  /**
+   * Allows disabling the CJK-friendly plugin.
+   * This plugin adds support for emphasis marks (**bold**) in Japanese, Chinese, and Korean text.
+   * @default true
+   * @see https://github.com/tats-u/markdown-cjk-friendly
+   */
+  cjkFriendly?: boolean
 }
 
 export type MarkdownRenderer = MarkdownItAsync
@@ -352,6 +360,10 @@ export async function createMarkdownRenderer(
     }
   }
 
+  if (options.cjkFriendly !== false) {
+    md.use(mditCjkFriendly)
+  }
+
   // apply user config
   if (options.config) {
     await options.config(md)