docs: add local auth screenshot

Author: manekinekko

docs/www/docs/cli/local-auth.md

@@ -9,6 +9,8 @@ The CLI allows to mock and read authentication and authorization credentials.
 
 When requesting the Static Web Apps login endpoints (`http://localhost:4280/.auth/login/<PROVIDER_NAME>`), you have access to a local authentication UI. This interface is served locally from the emulator and allows you to set fake user information for the current user from the provider supplied.
 
+![swa cli architecture](../../static/img/swa-cli-local-auth.png)
+
 ### Reading credentials
 
 The front-end application can request the `http://localhost:4280/.auth/me` endpoint and a `clientPrincipal` containing the fake information will be returned by the authentication API.