restore docs anchor js

docs/assets/js/src/application.js

@@ -76,3 +76,10 @@
   })
 
 }(jQuery)
+
+;(function () {
+  'use strict';
+
+  anchors.options.placement = 'left';
+  anchors.add('.bd-content > h1, .bd-content > h2, .bd-content > h3, .bd-content > h4, .bd-content > h5')
+})();