Update docs

Author: rmk135

docs/main/changelog.rst

@@ -7,6 +7,13 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+Development version
+------
+- Add support of default value for environment variable in INI and YAML
+  configuration files with ``${ENV_NAME:default}`` format.
+  See issue `#459 <https://github.com/ets-labs/python-dependency-injector/issues/459>`_.
+  Thanks to `Maksym Shemet @hbmshemet <https://github.com/hbmshemet>`_ for suggesting the feature.
+
 4.32.3
 ------
 - This fix a typo in ``di_in_python.rst`` doc.