Add lesson 3

- Add failing blog page test.
- Add custom routing, need to create Controller.
- Add BlogPageController.
- Test posts are visible.

web/modules/custom/example/src/Controller/BlogPageController.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Drupal\example\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+
+class BlogPageController extends ControllerBase {
+
+  public function __invoke(): array {
+    $nodeStorage = $this->entityTypeManager()->getStorage('node');
+    $nodes = $nodeStorage->loadMultiple();
+
+    $build = [];
+    $build['content']['#theme'] = 'item_list';
+    foreach ($nodes as $node) {
+      $build['content']['#items'][] = $node->label();
+    }
+
+    return $build;
+  }
+
+}