Add CHANGELOG entry for #471

Author: duckontheweb

CHANGELOG.md

@@ -4,10 +4,18 @@
 
 ### Added
 
-- Add a `preserve_dict` parameter to `ItemCollection.from_dict` and set it to False when using `ItemCollection.from_file`. ([#468](https://github.com/stac-utils/pystac/pull/468))
+- Add a `preserve_dict` parameter to `ItemCollection.from_dict` and set it to False when
+  using `ItemCollection.from_file`.
+  ([#468](https://github.com/stac-utils/pystac/pull/468)) 
+- `StacIO.json_dumps` and `StacIO.json_loads` methods for JSON
+  serialization/deserialization. These were "private" methods, but are now "public" and
+  documented ([#471](https://github.com/stac-utils/pystac/pull/471))
 
 ### Changed
 
+- `pystac.stac_io.DuplicateObjectKeyError` moved to `pystac.DuplicateObjectKeyError`
+  ([#471](https://github.com/stac-utils/pystac/pull/471))
+
 ### Fixed
 
 ### Removed