No external icon for _blank links in sidebar

[Chocobozzz]

Describe the bug

If using target: '_blank' for sidebar item, there is no icons indicating we leave the page

Reproduction

Create an external link in the sidebar:

"sidebar": {
    "/": {
      "text": "API",
      "items": [{ "text": "REST API reference", "link": "/api-rest-reference.html", "target": "_blank" }]
    }
  }

Expected behavior

Have an external link icon, like we had with pathname://...

System Info

vitepress v1.0.0-rc.31

Additional context

No response

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