add x448 to changelog (#4652)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 1801e04..191d804 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -21,6 +21,8 @@
   :class:`~cryptography.hazmat.primitives.hashes.SHA3_384`, and
   :class:`~cryptography.hazmat.primitives.hashes.SHA3_512` when using OpenSSL
   1.1.1.
+* Added support for :doc:`/hazmat/primitives/asymmetric/x448` when using
+  OpenSSL 1.1.1.
 * Added initial support for parsing PKCS12 files with
   :func:`~cryptography.hazmat.primitives.serialization.pkcs12.load_key_and_certificates`.
 * Added support for :class:`~cryptography.x509.IssuingDistributionPoint`.