added documentation

README.md

@@ -25,7 +25,7 @@ You will see that the django-prometheus plugin will expose general statistics li
 * HTTP response times,
 * CRUD operations on models that have been extended with the ```ExportModelOperationsMixin``` class.
 
-Example metric exposed by this plugin:
+Example metric exposed by this plugin (for a full list see ```example-exposed-metrics.txt```):
 
 ```
 # HELP django_model_inserts_total Number of insert operations by model.