Add link to changelog in readme

README.md

@@ -6,6 +6,7 @@
 - Plugins: http://www.fluentd.org/plugins
 - Time Format: http://ruby-doc.org/core-1.9.3/Time.html#method-i-strftime
 - Format Regex Editor: https://fluentular.herokuapp.com/
+- Changelog: https://support.treasuredata.com/hc/en-us/articles/360001479187-The-td-agent-ChangeLog
 
 # Preparing SSL Cert