ADD: scrolling to active TOC if TOC > viewport.

Scrolling to center active TOC element if TOC content is taller then viewport.

Author: ivan-nginx

source/js/src/post-details.js

@@ -17,6 +17,9 @@ $(document).ready(function () {
 
         removeCurrentActiveClass();
         $currentActiveElement.addClass('active-current');
+
+        // Scrolling to center active TOC element if TOC content is taller then viewport.
+        $tocElement.scrollTop($currentActiveElement.offset().top - $tocElement.offset().top + $tocElement.scrollTop() - ($tocElement.height() / 2));
       })
       .on('clear.bs.scrollspy', removeCurrentActiveClass);