docs: update CHANGELOG.md

Author: bednar

CHANGELOG.md

@@ -4,6 +4,7 @@
 1. [#281](https://github.com/influxdata/influxdb-client-python/pull/281): `FluxTable`, `FluxColumn` and `FluxRecord` objects have helpful reprs
 1. [#293](https://github.com/influxdata/influxdb-client-python/pull/293): `dataframe_serializer` supports batching
 1. [#301](https://github.com/influxdata/influxdb-client-python/pull/301): Add `proxy_headers` to configuration options
+1. [#306](https://github.com/influxdata/influxdb-client-python/pull/306): Supports `numpy` type in serialization to Line protocol
 
 ### Documentation
 1. [#301](https://github.com/influxdata/influxdb-client-python/pull/301): How to configure proxy