How to add additional field for products (displayed in the category list view)?

<?php
	if(hikashop_level(2) && !empty($this->productFields)) {
		$usefulFields = array();
		foreach ($this->productFields as $field) {
			$fieldname = $field->field_namekey;
			foreach($this->rows as $product) {
				if(!empty($product->$fieldname)) {
					$usefulFields[] = $field;
					break;
				}
			}
		}
		$productFields = $usefulFields;

		if(!empty($productFields)) {
			foreach($productFields as $field) {
				$columns++;
?>
					<th class="hikashop_product_field title hk_center"><?php
						echo $this->fieldsClass->getFieldName($field);
					?></th>
<?php
			}
		}
	}
?>

<?php
	if(hikashop_level(1) && !empty($productFields)) {
		foreach($productFields as $field) {
			$namekey = $field->field_namekey;
?>
						<td><?php
			if(!empty($field->field_products)) {
							$field_products = is_string($field->field_products) ? explode(',', trim($field->field_products, ',')) : $field->field_products;
							if(!in_array($this->row->product_id, $field_products))
								continue;
			}
			if(!empty($this->row->$namekey))
				echo '<p class="hikashop_product_field'.$namekey.'">'.$this->fieldsClass->show($field,$this->row->$namekey).'</p>';
						?></td>
<?php
		}
	}
?>