Update changelog

CHANGELOG.md

@@ -3,6 +3,11 @@
 #### Release Notes
 
 - Official packages built with Go 1.13.3.
+- The `prometheus` input and `prometheus_client` output have a new mapping to
+  and from Telegraf metrics, which can be enabled by setting `metric_version = 2`.
+  The original mapping is deprecated.  When both plugins have the same setting,
+  passthrough metrics will be unchanged.  Refer to the `prometheus` input for
+  details about the mapping.
 
 #### New Inputs
 
@@ -47,11 +52,13 @@
 - [#6680](https://github.com/influxdata/telegraf/pull/6668): Add support for sending HTTP Basic Auth in influxdb input
 - [#5767](https://github.com/influxdata/telegraf/pull/5767): Add ability to configure the url tag in the prometheus input.
 - [#5767](https://github.com/influxdata/telegraf/pull/5767): Add prometheus metric_version=2 mapping to internal metrics/line protocol.
+- [#6703](https://github.com/influxdata/telegraf/pull/6703): Add prometheus metric_version=2 support to prometheus_client output.
 - [#6660](https://github.com/influxdata/telegraf/pull/6660): Add content_encoding compression support to socket_listener.
 - [#6689](https://github.com/influxdata/telegraf/pull/6689): Add high resolution metrics support to CloudWatch output.
 - [#6716](https://github.com/influxdata/telegraf/pull/6716): Add SReclaimable and SUnreclaim to mem input.
 - [#6695](https://github.com/influxdata/telegraf/pull/6695): Allow multiple certificates per file in x509_cert input.
 - [#6686](https://github.com/influxdata/telegraf/pull/6686): Add additional tags to the x509 input.
+- [#6703](https://github.com/influxdata/telegraf/pull/6703): Add batch data format support to file output.
 
 #### Bugfixes