Add "external" icon to links to other domains (#324)

(cherry picked from commit 69d5727)

Author: adriendupuis

docs/js/custom.js

@@ -75,6 +75,12 @@ $(document).ready(function() {
         }
     });
 
+    $('.md-content a:not(.md-icon):not(.md-source):not(.instantsearch__entry)')
+        .filter(function() {
+            return this.hostname && this.hostname !== location.hostname;
+        })
+        .addClass('external');
+
     docsearch({
         container: '#docsearch',
         appId: 'WLX2XJZTRM',