ENGCOM-5725: Update Magento_AuthorizenetCardinal ReadMe #24327

 - Merge Pull Request #24327 from diazwatson/magento2:Magento_AuthorizenetCardinal_ReadMe
 - Merged commits:
   1. 68c2a5f
   2. 10ab3f2

Author: magento-engcom-team

app/code/Magento/AuthorizenetCardinal/README.md

@@ -1 +1,23 @@
-The AuthorizenetCardinal module provides a possibility to enable 3-D Secure 2.0 support for AuthorizenetAcceptjs payment integration.
+# Magento_AuthorizenetCardinal module
+
+Use the Magento_AuthorizenetCardinal module to enable 3D Secure 2.0 support for AuthorizenetAcceptjs payment integrations.
+
+## Structure
+
+`Gateway/` - the directory that contains payment gateway command interfaces and service classes.
+
+For information about typical file structure of a module in Magento 2, see [Module file structure](https://devdocs.magento.com/guides/v2.3/extension-dev-guide/build/module-file-structure.html#module-file-structure).
+
+## Extensibility
+
+Extension developers can interact with the Magento_AuthorizenetCardinal 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_AuthorizenetCardinal module.
+
+### Events
+   
+This module observes the following events:
+
+- `payment_method_assign_data_authorizenet_acceptjs` event in the `Magento\AuthorizenetCardinal\Observer\DataAssignObserver` 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).