Update Magento_Backup module ReadMe

Author: diazwatson

app/code/Magento/Backup/README.md

@@ -1,3 +1,28 @@
-The Backup module allows administrators to perform backups and rollbacks. Types of backups include system, database and media backups. This module relies on the Cron module to schedule backups.
+# Magento_Backup module
 
-This module does not affect the storefront.
+The Magento_Backup allows administrators to perform backups and rollbacks. Types of backups include system, database and media backups. This module relies on the Cron module to schedule backups.
+
+The Magento_Backup does not affect the storefront.
+
+For more information about this module, see [Magento Backups](https://docs.magento.com/m2/ce/user_guide/system/backups.html)
+
+## Extensibility
+
+Extension developers can interact with the Magento_Backup module. For more information about the Magento extension mechanism, see [Magento plug-ins](https://devdocs.magento.com/guides/v2.3/extension-dev-guide/plugins.html).
+
+[The Magento dependency injection mechanism](https://devdocs.magento.com/guides/v2.3/extension-dev-guide/depend-inj.html) enables you to override the functionality of the Magento_Backup module.
+
+### Layouts
+
+This module introduces the following layouts and layout handles in the `view/adminhtml/layout` directory:   
+
+`backup_index_block`
+`backup_index_disabled`
+`backup_index_grid`
+`backup_index_index`
+
+For more information about layouts in Magento 2, see the [Layout documentation](https://devdocs.magento.com/guides/v2.3/frontend-dev-guide/layouts/layout-overview.html).
+
+## Additional information
+
+For information about significant changes in patch releases, see [2.3.x Release information](https://devdocs.magento.com/guides/v2.3/release-notes/bk-release-notes.html).