Unable to support advanced features with code highlighting

[zce]

TL;DR

At present, some common advanced features of code highlighting plug-ins cannot work properly, such as highlighted lines.

Explains

Because the most of code-highlighting plug-ins implement these advanced features by code blocks meta, like this:

```js {1,3-4}
// highlighted-line
// 
console.log('foo') // highlighted-line
console.log('bar') // highlighted-line
```

But in Velite's markdown process, rehype-raw is used to process the rehype tree before loading the custom rehypePlugins.

However, rehype-raw will lead to the loss of metadata, refer to:

• code data fields be removed syntax-tree/hast-util-raw#13
• mdx codeblocks metadata doesn't apply changes withastro/astro#5163

[zce]

import { unified } from 'unified'
import rehypeRaw from 'rehype-raw'
import remarkParse from 'remark-parse'
import remarkRehype from 'remark-rehype'
import rehypeStringify from 'rehype-stringify'
import rehypePrettyCode from 'rehype-pretty-code'
import { inspect } from 'unist-util-inspect'

const text = `
<img src="https://example.com/image.png" alt="Example image" />

\`\`\`js {1}
import React from 'react'
\`\`\`
`

const file = await unified()
  .use(remarkParse)
  .use(remarkRehype, { allowDangerousHtml: true })
  .use(() => tree => console.log('before rehypeRaw', inspect(tree), '\n'))
  .use(rehypeRaw)
  .use(() => tree => console.log('after rehypeRaw', inspect(tree), '\n'))
  .use(rehypePrettyCode)
  .use(rehypeStringify)
  .process(text)

console.log(file.toString())