Backport PR #62396 on branch 2.3.x (PKG/DOC: indicate Python 3.14 support in pyproject.toml and release notes) (#62415)

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

Author: meeseeksmachine

doc/source/whatsnew/v2.3.3.rst

@@ -8,6 +8,17 @@ including other versions of pandas.
 
 {{ header }}
 
+.. _whatsnew_220.py14_compat:
+
+Pandas 2.3.3 is now compatible with Python 3.14
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Pandas 2.3.3 is the first version of pandas that is generally compatible with the upcoming
+Python 3.14, and both wheels for free-threaded and normal Python 3.14 will be uploaded for
+this release.
+
+As usual please report any bugs discovered to our `issue tracker <https://github.com/pandas-dev/pandas/issues/new/choose>`_
+
 .. ---------------------------------------------------------------------------
 .. _whatsnew_233.string_fixes:
 

pyproject.toml

@@ -49,6 +49,7 @@ classifiers = [
     'Programming Language :: Python :: 3.11',
     'Programming Language :: Python :: 3.12',
     'Programming Language :: Python :: 3.13',
+    'Programming Language :: Python :: 3.14',
     'Topic :: Scientific/Engineering'
 ]