gitlab-org--gitlab-foss/app/assets/stylesheets/fontawesome_custom.scss

// Custom Font Awesome styles that render emojis in asciidoc
.md {
  .fa {
    display: inline-block;
    font-style: normal;
    font-size: 14px;
    text-rendering: auto;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
  }

  .fa-2x {
    font-size: 2em;
  }

  .fa-exclamation-triangle::before {
    content: '⚠';
  }

  .fa-exclamation-circle::before {
    content: '❗';
  }

  .fa-lightbulb-o::before {
    content: '💡';
  }

  .fa-thumb-tack::before {
    content: '📌';
  }

  .fa-fire::before {
    content: '🔥';
  }

  .fa-square-o::before {
    content: '\2610';
  }

  .fa-check-square-o::before {
    content: '\2611';
  }
}