Update README.md

Changed auth-fallback to auth-mode
diff --git a/README.md b/README.md
index 9e0f2f8..a21f724 100644
--- a/README.md
+++ b/README.md
@@ -276,7 +276,7 @@
 })
 ```
     
-## Authentication, current user, and auth-fallback
+## Authentication, current user, and auth-mode
 
 ### appAuth and authenticateApp()