Update the GA4 usage example

README.md

@@ -348,11 +348,11 @@ function sendToGoogleAnalytics({name, delta, value, id}) {
   // Assumes the global `gtag()` function exists, see:
   // https://developers.google.com/analytics/devguides/collection/ga4
   gtag('event', name, {
-    // Use the metric delta as the event's value parameter.
-    value: delta,
-    // Everything below is a custom event parameter.
-    web_vitals_metric_id: id, // Needed to aggregate events.
-    web_vitals_metric_value: value, // Optional
+    // Built-in params:
+    value: value,
+    // Custom params:
+    metric_id: id, // Needed to aggregate events.
+    metric_delta: delta, // Optional
     // Any additional params or metadata (e.g. debug information) can be
     // set here as well, within the following limitations:
     // https://support.google.com/analytics/answer/9267744