fix: missing import for system-resource widget

Author: Meierschlumpf

docs/integrations/proxmox/index.mdx

@@ -12,6 +12,7 @@ import { IconHeartRateMonitor } from "@tabler/icons-react";
 import { proxmoxIntegration } from '.';
 import Alert from '@theme/Admonition'
 import { healthMonitoringWidget } from '@site/docs/widgets/health-monitoring';
+import { systemResourcesWidget } from '@site/docs/widgets/system-resources';
 
 <IntegrationHeader
   integration={proxmoxIntegration}