Backport PR #62257 on branch 2.3.x (DOC: Add release notes template for 2.3.3) (#62258)

Co-authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

Author: meeseeksmachine

doc/source/whatsnew/index.rst

@@ -16,6 +16,7 @@ Version 2.3
 .. toctree::
    :maxdepth: 2
 
+   v2.3.3
    v2.3.2
    v2.3.1
    v2.3.0

doc/source/whatsnew/v2.3.3.rst

@@ -0,0 +1,31 @@
+.. _whatsnew_233:
+
+What's new in 2.3.3 (September XX, 2025)
+----------------------------------------
+
+These are the changes in pandas 2.3.3. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_233.string_fixes:
+
+Improvements and fixes for the StringDtype
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Most changes in this release are related to :class:`StringDtype` which will
+become the default string dtype in pandas 3.0. See
+:ref:`whatsnew_230.upcoming_changes` for more details.
+
+.. _whatsnew_233.string_fixes.bugs:
+
+Bug fixes
+^^^^^^^^^
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_233.contributors:
+
+Contributors
+~~~~~~~~~~~~