docs(alerts): add Crashlytics onRegressionAlertPublished to README and example

Author: dackers86

README.md

@@ -519,6 +519,16 @@ firebase.alerts.crashlytics.onNewFatalIssuePublished(
   },
 );
 
+// Crashlytics regression alerts
+firebase.alerts.crashlytics.onRegressionAlertPublished(
+  (event) async {
+    final payload = event.data?.payload;
+    print('Regression: ${payload?.type}');
+    print('Issue: ${payload?.issue.title}');
+    print('Resolved: ${payload?.resolveTime}');
+  },
+);
+
 // Crashlytics non-fatal issues
 firebase.alerts.crashlytics.onNewNonfatalIssuePublished(
   (event) async {

example/alerts/bin/server.dart

@@ -23,6 +23,15 @@ void main(List<String> args) async {
       print('  App ID: ${event.appId}');
     });
 
+    // Crashlytics regression alert
+    firebase.alerts.crashlytics.onRegressionAlertPublished((event) async {
+      final payload = event.data?.payload;
+      print('Crashlytics regression:');
+      print('  Type: ${payload?.type}');
+      print('  Issue: ${payload?.issue.title}');
+      print('  Resolved: ${payload?.resolveTime}');
+    });
+
     // Crashlytics new non-fatal issue alert
     firebase.alerts.crashlytics.onNewNonfatalIssuePublished((event) async {
       final issue = event.data?.payload.issue;