Backport PR #2003: Add 4.3.1 to changelog

Signed-off-by: Min RK <benjaminrk@gmail.com>

docs/source/changelog.rst

@@ -11,6 +11,29 @@ For more detailed information, see `GitHub <https://github.com/jupyter/notebook>
      Use ``pip install notebook --upgrade`` or ``conda upgrade notebook`` to
      upgrade to the latest release.
      
+.. _release-4.3.1:
+
+4.3.1
+-----
+
+4.3.1 is a patch release with a security patch, a couple bug fixes, and improvements to the newly-released token authentication.
+
+Bug fixes:
+
+- Fix carriage return handling
+- Make the font size more robust against fickle brow
+- Ignore resize events that bubbled up and didn't come from window
+
+Other improvements:
+
+- Better docs for token-based authentication
+- Further highlight token info in log output when autogenerated
+- Add Authorization to allowed CORS headers
+
+See the 4.3 milestone on GitHub for a complete list of
+`issues <https://github.com/jupyter/notebook/issues?utf8=%E2%9C%93&q=is%3Aissue%20milestone%3A4.3.1%20>`__
+and `pull requests <https://github.com/jupyter/notebook/pulls?utf8=%E2%9C%93&q=is%3Apr%20milestone%3A4.3.1%20>`__ involved in this release.
+
 .. _release-4.3:
 
 4.3