Make documentation of * in function signatures easier to find

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-12-04.21:11:08.529>
labels = ['type-feature', '3.8', '3.9', '3.10', 'docs']
title = 'Make documentation of * in function signatures easier to find'
updated_at = <Date 2020-12-14.14:34:02.476>
user = 'https://github.com/fredg1'

bugs.python.org fields:

activity = <Date 2020-12-14.14:34:02.476>
actor = 'eric.araujo'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-12-04.21:11:08.529>
creator = 'fredg1'
dependencies = []
files = []
hgrepos = []
issue_num = 42571
keywords = []
message_count = 5.0
messages = ['382530', '382876', '382965', '382966', '382989']
nosy_count = 3.0
nosy_names = ['eric.araujo', 'docs@python', 'fredg1']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42571'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']