reference s3-objects-prune in README

Author: dvalentiate

README.md

@@ -28,6 +28,8 @@ With a `docker-compose` set up, this might look like the following:
     restart: always
 ```
 
-`PG_TO_S3_AWS_OBJECT_APPEND` and/or `PG_TO_S3_AWS_OBJECT_PREPEND` can be used to create a non guessable name if it is desired to have the database dump files stored in a non password protected bucket *(without list permissions)*. For instance having a UUID such as `PG_TO_S3_AWS_OBJECT_APPEND: _5761d557-f50d-4338-8c7e-a87318b95f87` would result in an S3 object similar like `2017-04-19_21:00_5761d557-f50d-4338-8c7e-a87318b95f87` being created. Or use a slash in the prepend value for a similar effect of `5761d557-f50d-4338-8c7e-a87318b95f87/2017-04-19_21:00`.
+`PG_TO_S3_AWS_OBJECT_APPEND` and/or `PG_TO_S3_AWS_OBJECT_PREPEND` can be used to create a non guessable name if it is desired to have the database dump files stored in a non password protected bucket *(without list permissions)*. For instance having a UUID such as `PG_TO_S3_AWS_OBJECT_APPEND: _5761d557-f50d-4338-8c7e-a87318b95f87` would result in an S3 object similar like `2017-04-19_21:00_5761d557-f50d-4338-8c7e-a87318b95f87` being created. Or use a slash in the prepend value for a similar effect of `5761d557-f50d-4338-8c7e-a87318b95f87/2017-04-19T21:00`.
 
 ***Note**: the usual cron tricks apply to the hour and minute env values. For instance setting `PG_TO_S3_CRON_HOUR` to `*/4` and `PG_TO_S3_CRON_MINUTE` to `0`, will trigger once every 4 hours.*
+
+Pruning the backups can be done with the `bluedrop360/s3-objects-prune` repo.