feat: add an example module with custom tests

Add a custom module based on my Drupal module template:

https://github.com/opdavies/drupal-module-template

web/modules/custom/example/example.services.yml

@@ -0,0 +1,7 @@
+services:
+  Drupal\Core\Logger\LoggerChannelFactoryInterface:
+    alias: logger.factory
+    private: true
+
+  Drupal\example\Controller\ExamplePageController:
+    autowire: true