Mention C++/Rust (Victor)

Co-authored-by: Victor Stinner <vstinner@python.org>

peps/pep-9999.rst

@@ -27,7 +27,7 @@ to the the acceptance of new designs of a more or less radical nature.
 The working group's mandate is to represent the interests of all Python users,
 but especially all maintainers of code that uses Python's C API,
 whether in the context of CPython, using an alternate Python implementation,
-or using a binding framework for other languages.
+or using a binding framework for other programming languages (such as C++ and Rust).
 
 The working group serves at the pleasure of the Python Steering Council.
 The working group's members are the listed authors of this PEP.