Add style for <kbd> element in markdown

Fixes #5825

CHANGELOG

@@ -62,6 +62,7 @@ v 7.11.0 (unreleased)
   - Call merge request web hook for each new commits (Arthur Gautier)
   - Use SIGKILL by default in Sidekiq::MemoryKiller
   - Fix mentioning of private groups.
+  - Add style for <kbd> element in markdown
 v 7.10.2
   - Fix CI links on MR page

app/assets/stylesheets/base/mixins.scss

@@ -73,6 +73,22 @@
     padding: 0;
   }
+  kbd {
+    display: inline-block;
+    padding: 3px 5px;
+    font-size: 11px;
+    line-height: 10px;
+    color: #555;
+    vertical-align: middle;
+    background-color: #FCFCFC;
+    border-width: 1px;
+    border-style: solid;
+    border-color: #CCC #CCC #BBB;
+    border-image: none;
+    border-radius: 3px;
+    box-shadow: 0px -1px 0px #BBB inset;
+  }
+
   h1 {
     margin-top: 45px;
     font-size: 2.5em;