Add websocket disconnect notification

Ref: https://github.com/harvester/harvester/issues/2186

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Verify Steps:

  1. Install Harvester with at least 2 nodes
  2. Login to Dashboard via Node IP
  3. Navigate to Advanced/Settings and update ui-index to https://releases.rancher.com/harvester-ui/dashboard/release-harvester-v1.0/index.html and force refresh to make it applied.
  4. restart the Node which holding the IP
  5. Notification of websocket disconnected should appeared