adding PEP references to documentation

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-09-14.22:49:01.149>
labels = ['docs']
title = 'adding PEP references to documentation'
updated_at = <Date 2020-09-16.03:26:47.313>
user = 'https://github.com/cameron-simpson'

bugs.python.org fields:

activity = <Date 2020-09-16.03:26:47.313>
actor = 'cameron'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-09-14.22:49:01.149>
creator = 'cameron'
dependencies = []
files = []
hgrepos = []
issue_num = 41787
keywords = ['patch']
message_count = 3.0
messages = ['376914', '376967', '376968']
nosy_count = 2.0
nosy_names = ['cameron', 'docs@python']
pr_nums = ['22269']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue41787'
versions = []