Update changelog to mention optional deps (#1885)

* Update changelog to mention optional deps

* Minor fix

* Minor fix

CHANGELOG.md

@@ -4,6 +4,22 @@
 
 v2.6.2 is a feature release with the following features, fixes and enhancements:
 
+Note: This release modifies the dependencies of the Schema Registry client. 
+If you are using the Schema Registry client, please ensure that you install the
+extra dependencies using the following syntax:
+
+```
+pip install confluent-kafka[schemaregistry]
+```
+
+or
+
+```
+pip install confluent-kafka[avro,schemaregistry]
+```
+
+Please see the [README.md](README.md) for more information.
+
  - Support for Data Contracts with Schema Registry, including
    - Data Quality rules
    - Data Transformation rules