Custom Page block fix (#2118)

Author: dabrt

docs/content_management/pages/create_custom_page_block.md

@@ -104,3 +104,6 @@ Place the edit template in `templates/themes/<your_theme>/blocks/event/config.ht
 ``` html+twig
 [[= include_file('code_samples/page/custom_page_block/templates/themes/standard/blocks/event/config.html.twig') =]]
 ```
+
+Your custom page block is now ready. 
+Before you can use it in Page Builder, you must [enable it in Page field settings]([[= user_doc =]]/content_management/configure_ct_field_settings/#block-display).