Fix PHPStan warnings

tasks/phpstan/bootstrap.php

@@ -4,3 +4,19 @@ define('ABSPATH', getenv('WP_ROOT') . '/');
 
 require_once ABSPATH . 'wp-load.php';
 require_once ABSPATH . 'wp-admin/includes/admin.php';
+
+function wc_get_customer_order_count(int $user_id): int {
+  return 0;
+}
+
+/**
+ * @param  mixed $order
+ * @return mixed
+ */
+function wc_get_order($order = false) {
+  return false;
+}
+
+function wc_price(float $price, array $args = []): string {
+  return '';
+}