externalLinkIcon isn't working

[AnilSonix]

Describe the bug

externalLinkIcon as true doesn't add the icon.

Reproduction

https://stackblitz.com/edit/vite-ysfhai?file=docs%2F.vitepress%2Fconfig.ts

Expected behavior

icon should be shown

System Info

System:
    OS: Windows 11 10.0.22621
    CPU: (4) x64 Intel(R) Core(TM) i5 CPU       M 520  @ 2.40GHz
    Memory: 2.15 GB / 7.93 GB
  Binaries:
    Node: 20.10.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.2.3 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Chromium (120.0.2210.121)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    vitepress: ^1.0.0-rc.35 => 1.0.0-rc.35

Additional context

No response

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.