Add footer to mails sent by GitHub Label Notifier

Change-Id: I6b441d9e3ce1362f3cb365ca39a1a869b21120e6
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/128590
Reviewed-by: William Hesse <whesse@google.com>
diff --git a/github-label-notifier/functions/node/index.dart b/github-label-notifier/functions/node/index.dart
index 7cc42ee..c7232d0 100644
--- a/github-label-notifier/functions/node/index.dart
+++ b/github-label-notifier/functions/node/index.dart
@@ -115,6 +115,8 @@
 <p><strong><a href="${issueUrl}">${escape(issueTitle)}</a>&nbsp;(${escape(repositoryName)}#${escape(issueNumber)})</strong></p>
 <p>Reported by <a href="${issueReporterUrl}">${escape(issueReporterUsername)}</a></p>
 <p>Labeled <strong>${escape(labelName)}</strong> by <a href="${senderUrl}">${escape(senderUser)}</a></p>
+<hr>
+<p>Sent by <a href="https://dart-github-label-notifier.web.app/">GitHub Label Notifier</a></p>
 ''');
 }