docs: add note about open-media-vault cpu-temps plugin (#197)

Author: latenightwreck

docs/integrations/hardware.mdx

@@ -13,6 +13,7 @@ The Dash. integration can be used to monitor the performance and used system res
 The OpenMediaVault integration allows you to view performance and resource data from your OpenMediaVault system. It is used by the following widgets:
 
 - [System Health Monitoring](/docs/widgets/health-monitoring)
+  - To use this widget, you must have the OpenMediaVault plugin `openmediavault-cputemp` installed.
 
 <details>
   <summary>