Add container base class

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 container base class ``containers.Container``. ``DynamicContainer``
+  and ``DeclarativeContainer`` become subclasses of the ``Container``.
+  See issue: `#386 <https://github.com/ets-labs/python-dependency-injector/issues/386>`_.
+  Thanks to `@ventaquil <https://github.com/ventaquil>`_ for reporting the issue.
+
 4.15.0
 ------
 - Add ``Configuration.from_pydantic()`` method to load configuration from a ``pydantic`` settings.