Backport PR #42312: DOC: Start v1.3.1 release notes (#42348)

Co-authored-by: Simon Hawkins <[email protected]>

Author: meeseeksmachine

doc/source/whatsnew/index.rst

@@ -16,6 +16,7 @@ Version 1.3
 .. toctree::
    :maxdepth: 2
 
+   v1.3.1
    v1.3.0
 
 Version 1.2

doc/source/whatsnew/v1.3.0.rst

@@ -1233,4 +1233,4 @@ Other
 Contributors
 ~~~~~~~~~~~~
 
-.. contributors:: v1.2.5..v1.3.0|HEAD
+.. contributors:: v1.2.5..v1.3.0

doc/source/whatsnew/v1.3.1.rst

@@ -0,0 +1,45 @@
+.. _whatsnew_131:
+
+What's new in 1.3.1 (July ??, 2021)
+-----------------------------------
+
+These are the changes in pandas 1.3.1. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_131.regressions:
+
+Fixed regressions
+~~~~~~~~~~~~~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_131.bug_fixes:
+
+Bug fixes
+~~~~~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_131.other:
+
+Other
+~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_131.contributors:
+
+Contributors
+~~~~~~~~~~~~
+
+.. contributors:: v1.3.0..v1.3.1|HEAD