Add external link icon with Hugo (using CSS)

layouts\partials\styles.html

<style>
  a[href^="http"]:not([href^="{{ (urls.Parse .Page.Permalink).Scheme }}://{{ (urls.Parse .Page.Permalink).Host }}"]):not(.no-external-icon)::after
    {
      content: 'launch';
      padding-left: 4px;
      position: inline-block;
      font-family: 'Material Icons';
      font-weight: normal;
      font-style: normal;
      font-size: 18px;
      /* display: inline-block; prevent nbsp bypass */
      line-height: 1;
      text-transform: none;
      letter-spacing: normal;
      word-wrap: normal;
      white-space: nowrap;
      direction: ltr;
      -webkit-font-smoothing: antialiased;
      text-rendering: optimizeLegibility;
      -moz-osx-font-smoothing: grayscale;
      font-feature-settings: 'liga';
      vertical-align: text-bottom;
    }
</style>