fix(rehype): default export use shared highlighter instance, fix #714

Author: antfu

docs/packages/rehype.md

@@ -38,6 +38,8 @@ const file = await unified()
   .process(await fs.readFile('./input.md'))
 ```
 
+The default export of `@shikijs/rehype` uses a shared instance of `shiki` from `getSingletonHighlighter`, which will persist across processes. If you want full control over the highlighter lifecycle, use [Fine-grained Bundle `@shikijs/rehype/core`](#fine-grained-bundle) instead.
+
 ## Fine-grained Bundle
 
 By default, the full bundle of `shiki` will be imported. If you are using a [fine-grained bundle](/guide/install#fine-grained-bundle), you can import `rehypeShikiFromHighlighter` from `@shikijs/rehype/core` and pass your own highlighter:

packages/rehype/src/index.ts

@@ -1,7 +1,8 @@
 /// <reference types="mdast-util-to-hast" />
+
 import type { LanguageInput } from 'shiki/core'
 import type { BuiltinLanguage, BuiltinTheme } from 'shiki'
-import { bundledLanguages, createHighlighter } from 'shiki'
+import { bundledLanguages, getSingletonHighlighter } from 'shiki'
 import type { Plugin } from 'unified'
 import type { Root } from 'hast'
 import rehypeShikiFromHighlighter from './core'
@@ -27,7 +28,7 @@ const rehypeShiki: Plugin<[RehypeShikiOptions], Root> = function (
 
   return async (tree) => {
     if (!getHandler) {
-      getHandler = createHighlighter({
+      getHandler = getSingletonHighlighter({
         themes: themeNames,
         langs,
       })