As described in its documentation, this adds a bot that does the following:
After a period of inactivity, a label will be applied to mark an issue as stale, and optionally a comment will be posted to notify contributors that the Issue or Pull Request will be closed.
If the Issue or Pull Request is updated, or anyone comments, then the stale label is removed and nothing further is done until it becomes stale again.
If no more activity occurs, the Issue or Pull Request will be automatically closed with an optional comment.
Please review this PR to set up its configuration.