Add Python 3.14 to the testing

[cclauss]

Python v3.14 -- October 7th

• https://www.python.org/download/pre-releases
• https://www.python.org/downloads/release/python-3140rc3
• https://docs.python.org/3.14/whatsnew/3.14.html

Like:

• add support for python 3.13 #347