Include matchedEvent variable (#8)

Author: benenharrington

docs/monitor-data/monitors.mdx

@@ -116,6 +116,8 @@ The URL will receive a HTTP(s) POST with a content type of `application/json`, t
 
 `.Value` — When the notification corresponds to a threshold monitor, this is the value that gave rise to the monitor triggering or resolving.
 
+`.MatchedEvent` — When the notification corresponds to a match monitor, this is the event that gave rise to the monitor matching.
+
 You can use the Go Template syntax to interact with these variables when defining a custom body for your webhook.
 
 A sample webhook body is shown below. This applies the default template shown on creating a custom webhook to a sample notification generated from a threshold monitor triggering.
@@ -131,7 +133,8 @@ A sample webhook body is shown below. This applies the default template shown on
     "queryStartTime": "2024-06-28 14:45:57.631364493 +0000 UTC",
     "timestamp": "2024-06-28 14:55:57 +0000 UTC",
     "title": "Axiom Monitor Test Triggered",
-    "value": 57347
+    "value": 57347,
+    "matchedEvent": null
   }
 }
 ```