PEP 791: address PEP review comments

* add submodule variant

Author: skirpichev

peps/pep-0791.rst

@@ -131,6 +131,10 @@ interval math or numerical integration.
 Other proposed names include ``ntheory`` (like SymPy's submodule),
 ``integermath`` and ``imaths``.
 
+As a variant, new module can be added as a submodule of the
+:external+py3.14:mod:`math`.  The main module itself will preserve "catch-all"
+role for mathematics in the stdlib.
+
 
 Module scope and possible extensions
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