Add a mention to the CHANGELOG.

Author: Julian

CHANGELOG.rst

@@ -1,3 +1,14 @@
+v4.9.0
+------
+
+* ``pkgutil.resolve_name`` is now used to retrieve validators
+  provided on the command line. This function is only available on
+  3.9+, so 3.7 and 3.8 (which are still supported) now rely on the
+  `pkgutil_resolve_name <https://pypi.org/project/pkgutil_resolve_name/>`_
+  backport package. Note however that the CLI itself is due
+  to be deprecated shortly in favor of `check-jsonschema
+  <https://github.com/python-jsonschema/check-jsonschema>`_.
+
 v4.8.0
 ------