make background of table-of-content lighter

Author: martin-henz

static/assets/stylesheet.css

@@ -12947,7 +12947,7 @@ html * {
 }
 
 #nav-sidebar {
-  background-color: #333333f5;
+  background-color: #888888f5;
   position: fixed;
   top: 46px;
   left: 0px;