Document volume alerting webhook

Author: paulocsanz

src/docs/guides/webhooks.md

@@ -16,7 +16,7 @@ Complete the following steps to setup a webhook:
 4. Input your desired webhook URL.
 5. Click `Save Webhook`.
 
-The URL you provide will receive a webhook payload when any service's deployment status changes. This will be executed across all environments in the project.
+The URL you provide will receive a webhook payload when any service's deployment status changes or an alert is triggered. This will be executed across all environments in the project.
 
 To see what payload will be transmitted to the URL, you can expand the "Example webhook payload" panel.
 

src/docs/reference/webhooks.md

@@ -11,10 +11,18 @@ width={823} height={324} quality={80} />
 
 ## How it Works
 
+### Deployment Status
+
 When a deployment's status changes, Railway will send a notification via HTTP to the URL provided in the webhook configuration.
 
 Deployment states can be found [here](/reference/deployments#deployment-states).
 
+### Alerts
+
+When a volume usage breaches certain thresholds, Railway will send a notification to pro customers via HTTP to the URL provided in the webhook configuration.
+
+The thresholds that alert can be configured in the volume settings page.
+
 ## Muxers
 
 Webhooks contain Muxers which will automatically identify webhook URLs and transform the payload based on where it's going. Below are the currently supported Muxers:
@@ -23,4 +31,4 @@ Webhooks contain Muxers which will automatically identify webhook URLs and trans
 
 ## Setting up a webhook
 
-For information on how to setup webhooks, visit [this guide](/guides/webhooks).
+For information on how to setup webhooks, visit [this guide](/guides/webhooks).