Adding Nucleo custom font icons

custom.php

/**
  * Add Custom Nucleo Font Icons to Shiftnav Plugin
  */
add_action( 'shiftnav_register_icons' , 'nucleo_custom_icons' , 20 );
function nucleo_custom_icons(){
   if( !function_exists( 'shiftnav_register_icons' ) ) return;
   shiftnav_register_icons( 'nucleo' , array(
      'title' => 'KE_icon_font',
      'class_prefix' => 'nc-',
      'iconmap' => array(
         'minimal-down' => array(
            'title' => 'Minimal Down',
         ),
         'minimal-up' => array(
            'title' => 'Minimal Up',
         ),
         'delivery-truck' => array(
            'title' => 'Delivery Truck',
         ),
         //list additional icons to register
      )
   ));
}