add example to change navbar height variable via css

Author: lenadax

examples/cone.example/src/cone/example/browser/static/cone.example.css

@@ -44,3 +44,8 @@ tr.state-private td.title a {
 tr.state-public td.title a {
     color: green;
 }
+
+
+:root {
+    /* --navbar-height: 100px; */ /* Example of custom navbar height */
+}