Fix compatibility with Lumen (#1043)

* Fix compatibility with Lumen

Fixes https://github.com/barryvdh/laravel-ide-helper/issues/1042

Got broken by https://github.com/barryvdh/laravel-ide-helper/pull/1026

TL;DR: can't use anything in the `Illuminate\Foundation` namespace
without safety check, as it doesn't exist in Lumen.

* Add helper to check for Laravel

* Use helper to check for Laravel

src/Helpers.php

@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper;
+
+class Helpers
+{
+    public static function isLaravel(): bool
+    {
+        return class_exists('Illuminate\Foundation\Application');
+    }
+}

src/IdeHelperServiceProvider.php

@@ -110,7 +110,7 @@ class IdeHelperServiceProvider extends ServiceProvider implements DeferrableProv
     {
         $resolver = new EngineResolver();
         $resolver->register('php', function () {
-            if ((int) Application::VERSION < 8) {
+            if (Helpers::isLaravel() && (int) Application::VERSION < 8) {
                 return new PhpEngine();
             }