Added note for debugging with serve configurations (SharePoint#2179)

Author: thechriskent

docs/spfx/extensions/guidance/migrate-from-ecb-to-spfx-extensions.md

@@ -202,6 +202,8 @@ To reproduce the same behavior of the ECB menu item built by using the SharePoin
 
   Notice that when executing the page request, you are prompted with a warning message box with the title "Allow debug scripts?", which asks your consent to run code from localhost for security reasons. Of course, if you want to locally debug and test the solution, you have to allow it to "Load debug scripts."
 
+> Alternatively, you can create serve configuration entries in the `config/serve.json` file in your project to automate the creation of the debug query string parameters as outlined in this document: [Debug SharePoint Framework solutions on modern SharePoint pages](https://docs.microsoft.com/en-us/sharepoint/dev/spfx/debug-modern-pages#debug-sharepoint-framework-extensions-on-modern-sharepoint-pages)
+
 <a name="PackageAndHostCommandSet"> </a>
 
 ## Package and host the solution