Enable pydoc to run as background job

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-03-03.13:34:22.003>
labels = ['type-feature', 'library', '3.10']
title = 'Enable pydoc to run as background job'
updated_at = <Date 2021-03-06.01:04:07.953>
user = 'https://bugs.python.org/digitaldragon'

bugs.python.org fields:

activity = <Date 2021-03-06.01:04:07.953>
actor = 'terry.reedy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-03-03.13:34:22.003>
creator = 'digitaldragon'
dependencies = []
files = []
hgrepos = []
issue_num = 43387
keywords = []
message_count = 1.0
messages = ['388017']
nosy_count = 1.0
nosy_names = ['digitaldragon']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43387'
versions = ['Python 3.10']