Enable display of admonition icons in Asciidoc.

When rendering Asciidoc documents this merge request enables the diplay of
admonition blocks using font icons. This improves the looks of Asciidoc redered
files.

This uses the font-awesome fonts already present in Gitlab so no large
dependencies are required for this to work.

app/assets/stylesheets/framework.scss

@@ -6,6 +6,7 @@
 
 @import "framework/animations.scss";
 @import "framework/avatar.scss";
+@import "framework/asciidoctor.scss";
 @import "framework/blocks.scss";
 @import "framework/buttons.scss";
 @import "framework/calendar.scss";

app/assets/stylesheets/framework/asciidoctor.scss

+.admonitionblock td.icon {
+  width: 1%;
+
+  [class^="fa icon-"] {
+    @extend .fa-2x;
+  }
+
+  .icon-note {
+    @extend .fa-thumb-tack;
+  }
+
+  .icon-tip {
+    @extend .fa-lightbulb-o;
+  }
+
+  .icon-warning {
+    @extend .fa-exclamation-triangle;
+  }
+
+  .icon-caution {
+    @extend .fa-fire;
+  }
+
+  .icon-important {
+    @extend .fa-exclamation-circle;
+  }
+}

changelogs/unreleased/enable-asciidoctor-admonition-icons.yml

+---
+title: Enable AsciiDoctor admonition icons
+merge_request: 7812
+author: Horacio Sanson

lib/gitlab/asciidoc.rb

@@ -6,7 +6,7 @@ module Gitlab
   module Asciidoc
     DEFAULT_ADOC_ATTRS = [
       'showtitle', 'idprefix=user-content-', 'idseparator=-', 'env=gitlab',
-      'env-gitlab', 'source-highlighter=html-pipeline'
+      'env-gitlab', 'source-highlighter=html-pipeline', 'icons=font'
     ].freeze
 
     # Public: Converts the provided Asciidoc markup into HTML.