ENGCOM-5921: Update Magento_BraintreeGraphQl module ReadMe #24680

 - Merge Pull Request #24680 from diazwatson/magento2:ReadMe_Magento_BraintreeGraphQl
 - Merged commits:
   1. 1429078
   2. a98d74a
   3. 6b2e747

Author: magento-engcom-team

app/code/Magento/BraintreeGraphQl/README.md

@@ -1,4 +1,9 @@
-# BraintreeGraphQl
+# Magento_BraintreeGraphQl module
 
-**BraintreeGraphQl** provides type and resolver for method additional
-information.
+The Magento_BraintreeGraphQl module provides type and resolver information for the GraphQL module to pass payment information data from the client to Magento.
+
+## Extensibility
+
+Extension developers can interact with the Magento_BraintreeGraphQl 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_BraintreeGraphQl module.