Add example of migrating existing users

docs/LARAVEL_USAGE.md

@@ -33,7 +33,7 @@ authenticated through the OIDC provider. The event is passed the fields
 returned by the OIDC provider (e.g., email, name).
 
 If a listener is registered, it is expected to return an instance of your User
-model, initialized and saves, that will be tied to the OIDC ID the user has
+model, initialized and saved, that will be tied to the OIDC ID the user has
 authenticated with.
 
 For example, a minimal implementation to recreate the default behaviour would