Update README webhook configuration with plist format example

Replace plain URL with proper plist dictionary format showing both
started and finished webhook keys. Add note about missing keys
preventing webhook delivery.

Author: motionbug

README.md

@@ -101,9 +101,19 @@ id = "paste-your-id-here"
 In your Setup Manager configuration, set the webhook URL to:
 
 ```
-https://setup-manager-hud.<your-subdomain>.workers.dev/webhook
+<key>webhooks</key>
+<dict>
+  <key>finished</key>
+  <string>https://setup-manager-hud.<your-subdomain>.workers.dev/webhook</string>
+  <key>started</key>
+  <string>https://setup-manager-hud.<your-subdomain>.workers.dev/webhook</string>
+</dict>
 ```
 
+Remember when either the started or finished key is missing, no webhook will be sent for that event.
+
+
+
 Setup Manager will POST enrollment events to this endpoint. They'll appear on the dashboard in real-time.
 
 > **Note:** The `/webhook` endpoint is excluded from authentication (see below) so devices can POST without credentials.