added error code 90070

Author: niklashaggstrom

nav/_operation/working-with-alerts.md

@@ -125,6 +125,7 @@ When *Nodes* come offline a workflow will be triggered which does the following:
 | **90050** | High memory utilization | 
 | **90060** | Failed to start snap | 
 | **90061** | Snap crash | 
+| **90070** | High cpu utilization | 
 | **90100** | Failed to start docker container | 
 | **90101** | Docker containers crash | 
 | **90102** | Custom docker log event |