Restoring onStart() function to menu menu partial

Code determines which section of the site is current and applies the relevant classes to the menu items

www/themes/jason-williamsca/partials/mainmenu.htm

@@ -1,5 +1,13 @@
 description = "Main Site Menu"
 ==
+<?php
+function onStart()
+{
+    // Determine the acive section of the site in order to customize the navigation
+    $this['activeSection'] = explode('/', $_SERVER['REQUEST_URI'])[1];
+}
+?>
+==
 <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
     <span class="navbar-toggler-icon"></span>
 </button>