Add PR health workflow (#141)

* Add PR health workflow

* Fix branch name

* Add missing license

.github/workflows/health.yaml

@@ -0,0 +1,15 @@
+name: Health
+
+on:
+  pull_request:
+    branches: [ master ]
+    types: [opened, synchronize, reopened, labeled, unlabeled]
+
+jobs:
+  health:
+    uses: dart-lang/ecosystem/.github/workflows/health.yaml@main
+    with:
+      coverage_web: false
+      sdk: dev
+    permissions:
+      pull-requests: write

.github/workflows/post_summaries.yaml

@@ -0,0 +1,17 @@
+name: Comment on the pull request
+
+on:
+  # Trigger this workflow after the Health workflow completes. This workflow will have permissions to
+  # do things like create comments on the PR, even if the original workflow couldn't.
+  workflow_run:
+    workflows: 
+      - Health
+      - Publish
+    types:
+      - completed
+
+jobs:
+  upload:
+    uses: dart-lang/ecosystem/.github/workflows/post_summaries.yaml@main
+    permissions:
+      pull-requests: write

example/display_headers.dart

@@ -1,3 +1,7 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';