update changelog

Author: jpadilla

CHANGELOG.rst

@@ -13,6 +13,19 @@ Changed
 - Use ``Sequence`` for parameter types rather than ``List`` where applicable by @imnotjames in `#970 <https://github.com/jpadilla/pyjwt/pull/970>`__
 - Remove algorithm requirement from JWT API, instead relying on JWS API for enforcement, by @luhn in `#975 <https://github.com/jpadilla/pyjwt/pull/975>`__
 - Add JWK support to JWT encode by @luhn in `#979 <https://github.com/jpadilla/pyjwt/pull/979>`__
+- Encoding and decoding payloads using the `none` algorithm
+
+  Before:
+
+  ```
+  jwt.encode({"payload":"abc"}, key=None, algorithm=None)
+  ```
+
+  After:
+
+  ```
+  jwt.encode({"payload":"abc"}, key=None, algorithm='none')
+  ```
 
 Fixed
 ~~~~~