critical alerts: waiting jobs in queue (#732)

docs/core_concepts/37_critical_alert_channels/index.mdx

@@ -14,6 +14,7 @@ Critical alerts are generated under the following conditions:
 - [License key](../../misc/7_plans_details/index.mdx#using-the-license-key-self-host) does not renew.
 - [Workspace error handler](../10_error_handling/index.mdx#workspace-error-handler) fails.
 - Number of running workers in a group falls below a specified threshold (has to be configured in the [worker group](../9_worker_groups/index.mdx) config).
+- Number of [jobs waiting in queue](../9_worker_groups/index.mdx#queue-metric-alerts) is above a threshold for more than a specified amount of time.
 
 You just need to [configure SMTP](../../advanced/1_self_host/index.mdx#set-up-smtp-from-the-ui) and setup a critical alert channel (aka email address) in the [instance settings](../../advanced/18_instance_settings/index.mdx#smtp) or connect your instance to Slack and fill in a channel name.
 

docs/core_concepts/9_worker_groups/index.mdx

@@ -321,6 +321,10 @@ Only tags for jobs that have been delayed by more than 3 seconds in the last 14
 
 ![Queue Metrics](./queue_metrics.png 'Queue Metrics')
 
+### Queue Metric Alerts
+Enterprise Edition users can set up [Critical Alerts](../37_critical_alert_channels/index.mdx) on the [Queue Metrics page](#queue-metrics), and be notified when the number of delayed jobs in a queue is above a certain threshold for more than a configured amount of time. The "cooldown" parameter determines the minimum duration between two consecutive alerts if the number of waiting jobs are fluctuating around the configured threshold.
+
+![Queue Metrics](./queue_metrics_alert.png 'Queue Metrics Alert')
 ## Workers and vCPUs
 
 Even though Windmill's architecture relies on workers, Windmill's [pricing](/pricing) is vCPU-based. For example, 4 workers with 0.25 vCPU each is 1 vCPU. 1 worker with 4 vCPU would count as 4 vCPU. But if it only runs for 1h every day, you would divide that by 24. Each vCPU can run up to ~26M jobs per month.