ENGCOM-5920: Update Magento_Braintree module ReadMe #24679

 - Merge Pull Request #24679 from diazwatson/magento2:ReadMe_Magento_Braintree
 - Merged commits:
   1. 02ac878
   2. a75934b

Author: magento-engcom-team

app/code/Magento/Braintree/README.md

@@ -1 +1,47 @@
-Module Magento\Braintree implements integration with the Braintree payment system.
+# Magento_Braintree module
+
+The Magento_Braintree module implements integration with the Braintree payment system.
+
+## Extensibility
+
+Extension developers can interact with the Magento_Braintree 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_Braintree module.
+
+### Events
+
+This module observes the following events:
+
+ - `payment_method_assign_data_braintree` event in `Magento\Braintree\Observer\DataAssignObserver` file.
+ - `payment_method_assign_data_braintree_paypal` event in `Magento\Braintree\Observer\DataAssignObserver` file.
+ - `shortcut_buttons_container` event in `Magento\Braintree\Observer\AddPaypalShortcuts` file.
+
+For information about an event in Magento 2, see [Events and observers](https://devdocs.magento.com/guides/v2.3/extension-dev-guide/events-and-observers.html#events).
+
+### Layouts
+
+This module interacts with the following layouts and layout handles in the `view/adminhtml/layout` directory:
+
+- `braintree_paypal_review`
+- `checkout_index_index`
+- `multishipping_checkout_billing`
+- `vault_cards_listaction`
+
+This module interacts with the following layout handles in the `view/frontend/layout` directory:
+
+- `adminhtml_system_config_edit`
+- `braintree_report_index`
+- `sales_order_create_index`
+- `sales_order_create_load_block_billing_method`
+
+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).
+
+### UI components
+
+You can extend admin notifications using the `view/adminhtml/ui_component/braintree_report.xml` configuration file.
+
+For information about UI components in Magento 2, see [Overview of UI components](https://devdocs.magento.com/guides/v2.3/ui_comp_guide/bk-ui_comps.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).