Add notification (#2241)

* add cron notify

* fix format

* fix format

notify/mail.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env sh
+
+# support local mail app
+
+mail_send() {
+  _subject="$1"
+  _content="$2"
+  _statusCode="$3" #0: success, 1: error 2($RENEW_SKIP): skipped
+  _debug "_subject" "$_subject"
+  _debug "_content" "$_content"
+  _debug "_statusCode" "$_statusCode"
+
+  _err "Not implemented yet."
+  return 1
+}