Cover directory and zipfile execution in __main__ module docs

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-09-09.07:45:42.475>
labels = ['type-feature', 'docs']
title = 'Cover directory and zipfile execution in __main__ module docs'
updated_at = <Date 2022-03-11.14:52:45.711>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2022-03-11.14:52:45.711>
actor = 'petr.viktorin'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2021-09-09.07:45:42.475>
creator = 'ncoghlan'
dependencies = []
files = []
hgrepos = []
issue_num = 45149
keywords = []
message_count = 1.0
messages = ['401440']
nosy_count = 2.0
nosy_names = ['ncoghlan', 'docs@python']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue45149'
versions = []