Prevent padding from causing horizontal scolling too early

Author: p01

src/resource-manager/resource_style.css

@@ -279,6 +279,7 @@ a.external:hover
 
 .resource-tree li > h2
 {
+  box-sizing: border-box;
   margin: 0;
   padding: 0 4px;
   white-space: nowrap;