Add config-file alias

Author: rcthomas

jupyterhub_idle_culler/__init__.py

@@ -655,6 +655,7 @@ def _log_format_default(self):
     aliases = {
         "api-page-size": "IdleCuller.api_page_size",
         "concurrency": "IdleCuller.concurrency",
+        "config-file": "IdleCuller.config_file",
         "cull-admin-users": "IdleCuller.cull_admin_users",
         "cull-default-servers": "IdleCuller.cull_default_servers",
         "cull-every": "IdleCuller.cull_every",