Add scroll padding for anchor links on mobile

As the menu bar is fixed and overlaps the content we need to add scroll
padding for the links to be visible.

Author: p8

lib/rdoc/generator/template/rails/resources/css/panel.css

@@ -5,6 +5,10 @@
     }
 
     @media (max-width: 599px) {
+        html {
+            scroll-padding-top: 50px;
+        }
+
         .panel_mobile_button {
             display: block;
             height: 40px;