update contributing guide

Author: parthea

CONTRIBUTING.rst

@@ -21,7 +21,7 @@ In order to add a feature:
   documentation.
 
 - The feature must work fully on the following CPython versions:
-  3.7, 3.8, 3.9, 3.10, 3.11, 3.12 and 3.13 on both UNIX and Windows.
+  3.7, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13 and 3.14 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -204,6 +204,7 @@ We support:
 -  `Python 3.11`_
 -  `Python 3.12`_
 -  `Python 3.13`_
+-  `Python 3.14`_
 
 .. _Python 3.7: https://docs.python.org/3.7/
 .. _Python 3.8: https://docs.python.org/3.8/
@@ -212,6 +213,7 @@ We support:
 .. _Python 3.11: https://docs.python.org/3.11/
 .. _Python 3.12: https://docs.python.org/3.12/
 .. _Python 3.13: https://docs.python.org/3.13/
+.. _Python 3.14: https://docs.python.org/3.14/
 
 
 Supported versions can be found in our ``noxfile.py`` `config`_.