Make 'rt' the default for open in docs

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-04-24.20:16:00.259>
labels = ['type-feature', '3.9', 'docs']
title = "Make 'rt' the default for open in docs"
updated_at = <Date 2020-05-01.20:43:05.171>
user = 'https://github.com/facundobatista'

bugs.python.org fields:

activity = <Date 2020-05-01.20:43:05.171>
actor = 'terry.reedy'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-04-24.20:16:00.259>
creator = 'facundobatista'
dependencies = []
files = []
hgrepos = []
issue_num = 40382
keywords = []
message_count = 2.0
messages = ['367219', '367885']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'facundobatista', 'docs@python']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue40382'
versions = ['Python 3.9']