message: docs(theme): improve icon
diff: .theme-hope-content a {
  + &[href*="github.com/"],
  + &[href*=".vuejs.org/"],
  &[href*="/v2/blog/"],
  &[href*="/v2/comment/"],
  &[href*="/v2/components/"],
  }
  }
  + &[href*="github.com/"]::before {
  + content: "\e653";
  + }
  +
  + &[href*=".vuejs.org/"]::before {
  + content: "\f25f";
  + }
  +
  &[href*="/v2/blog/"]::before {
  content: "\e655";
  }
  &[href*="/guide/advanced/"]::before {
  content: "\e77c";
  }
  -
  - &[href^="https://v2.vuepress.vuejs.org/"]::before
  - {
  - content: "\f25f";
  - }
  }
  