DOC: add whatsnew for 2.1.4 (#55924)

Author: lukemanley

doc/source/whatsnew/index.rst

@@ -24,6 +24,7 @@ Version 2.1
 .. toctree::
    :maxdepth: 2
 
+   v2.1.4
    v2.1.3
    v2.1.2
    v2.1.1

doc/source/whatsnew/v2.1.4.rst

@@ -0,0 +1,41 @@
+.. _whatsnew_214:
+
+What's new in 2.1.4 (December ??, 2023)
+---------------------------------------
+
+These are the changes in pandas 2.1.4. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_214.regressions:
+
+Fixed regressions
+~~~~~~~~~~~~~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_214.bug_fixes:
+
+Bug fixes
+~~~~~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_214.other:
+
+Other
+~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_214.contributors:
+
+Contributors
+~~~~~~~~~~~~
+
+.. contributors:: v2.1.3..v2.1.4|HEAD