[finder] Add stub for Finder (#211)

Author: VincentLanglet

src/Stubs/common/Component/Finder/Finder.stubphp

@@ -0,0 +1,13 @@
+<?php
+
+namespace Symfony\Component\Finder;
+
+use Countable;
+use IteratorAggregate;
+
+/**
+ * @implements IteratorAggregate<string, \SplFileInfo>
+ */
+class Finder implements IteratorAggregate, Countable
+{
+}

tests/acceptance/acceptance/Finder.feature

@@ -0,0 +1,28 @@
+@symfony-common
+Feature: Finder
+
+  Background:
+    Given I have Symfony plugin enabled
+
+  Scenario: Finder should be considered as an IteratorAggregate of SplFileInfo
+    Given I have the following code
+      """
+      <?php
+
+      use Symfony\Component\Finder\Finder;
+
+      class Test
+      {
+          /**
+           * @param iterable<SplFileInfo> $files
+           */
+          public static function run(iterable $files): void
+          {
+          }
+      }
+
+      $finder = new Finder();
+      Test::run($finder);
+      """
+    When I run Psalm
+    Then I see no errors