[Docs][BootstrapAdminUi] Copy usage with Sylius resource package (#301)

We already have this example code here

https://github.com/Sylius/Stack/blob/main/docs/admin-ui/getting-started.md#crud-templates

But to ensure that users find the information, we can also adding it
here.

https://stack.sylius.com/~/revisions/NuG6wpwKbLILmM1LB1yz/bootstrap-admin-ui/getting-started#configuring-the-crud-templates

Author: loic425

docs/bootstrap-admin-ui/getting-started.md

@@ -21,6 +21,27 @@ CRUD templates are split into configurable blocks.
 
 You can add new blocks, disable existing ones, or reorder them using the [TwigHooks package](../twig-hooks/getting-started.md).
 
+### Usage with the Sylius Resource package
+
+{% code title="src/Entity/Speaker.php" lineNumbers="true" %}
+```php
+namespace App\Entity;
+
+use Sylius\Resource\Metadata\AsResource;
+use Sylius\Resource\Model\ResourceInterface;
+
+#[AsResource(
+    // We still use the Sylius admin ui templates dir.
+    templatesDir: '@SyliusAdminUi/crud', 
+)]
+class Speaker implements ResourceInterface
+{
+    // ...
+}
+
+```
+{% endcode %}
+
 ### Create
 
 This package sets up the template content needed to create a new resource.