README: note Python 3.14 support

Author: mr-c

README.rst

@@ -32,7 +32,7 @@ This is a testing tool for checking the output of Tools and Workflows described
 with the Common Workflow Language.  Among other uses, it is used to run the CWL
 conformance tests.
 
-This is written and tested for Python 3.9, 3.10, 3.11, 3.12, and 3.13.
+This is written and tested for Python 3.9, 3.10, 3.11, 3.12, 3.13, and 3.14
 
 .. contents:: Table of Contents
    :local: