Fix anchor focus styling for markdown headings

app/assets/stylesheets/framework/typography.scss

@@ -458,7 +458,7 @@
   h6 {
     a.anchor {
       float: left;
-      margin-left: -16px;
+      margin-left: -20px;
       text-decoration: none;
       outline: none;
 
@@ -471,6 +471,11 @@
     &:hover > a.anchor::after {
       visibility: visible;
     }
+
+    > a.anchor:focus::after {
+      visibility: visible;
+      outline: auto;
+    }
   }
 
   .big {