Include theme-settings.php

Fixes #108

Author: mglaman

src/Drupal/DrupalAutoloader.php

@@ -133,6 +133,11 @@ public function register(Container $container): void
         }
         foreach ($this->themeData as $extension) {
             $this->loadExtension($extension);
+            $theme_dir = $this->drupalRoot . '/' . $extension->getPath();
+            $theme_settings_file = $theme_dir . '/theme-settings.php';
+            if (file_exists($theme_settings_file)) {
+                $this->loadAndCatchErrors($theme_settings_file);
+            }
         }
 
         if (class_exists(\Drush\Drush::class)) {

tests/src/DrupalIntegrationTest.php

@@ -66,4 +66,9 @@ public function testAppRootPseudoService() {
         $errors = $this->runAnalyze(__DIR__ . '/../fixtures/drupal/modules/phpstan_fixtures/src/AppRootParameter.php');
         $this->assertCount(0, $errors, var_export($errors, TRUE));
     }
+
+    public function testThemeSettingsFile() {
+        $errors = $this->runAnalyze(__DIR__ . '/../fixtures/drupal/core/modules/system/tests/themes/test_theme_settings/theme-settings.php');
+        $this->assertCount(0, $errors, var_export($errors, TRUE));
+    }
 }