Update changelog

Author: danielnelson

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 - [bind](/plugins/inputs/bind/README.md) - Contributed by @dswarbrick & @danielllek
 - [github](/plugins/inputs/github/README.md) - Contributed by @influxdata
+- [powerdns_recursor](/plugins/inputs/powerdns_recursor/README.md) - Contributed by @dupondje
 
 #### New Serializers