address review: add "How to Teach This"

Author: skirpichev

peps/pep-0791.rst

@@ -78,6 +78,21 @@ As aliases in :external+py3.14:mod:`math` will be kept for an indefinite time
 (their use would be discouraged), there are no anticipated code breaks.
 
 
+How to Teach This
+=================
+
+The new module will be a place to functions, that 1) accept
+:external+py3.14:class:`int`-like arguments and return also integers, 2) are
+also in the field of arbitrary-precision integer arithmetic, i.e. have no
+dependence on the platform floating-point format or behaviour and/or on the
+platorm math library (``libm``).
+
+For users it would be natural first to look on the
+:external+py3.14:class:`int`'s methods, which cover most basic use-cases (e.g.
+:external+py3.14:meth:`int.bit_length` method), than to some dedicated place in
+the stdlib.
+
+
 Reference Implementation
 ========================