Allow users to set suffix list in cookiejar policy

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-12-30.15:37:18.396>
labels = ['3.8', 'type-feature', 'library']
title = 'Allow users to set suffix list in cookiejar policy'
updated_at = <Date 2019-03-24.18:53:49.706>
user = 'https://github.com/tirkarthi'

bugs.python.org fields:

activity = <Date 2019-03-24.18:53:49.706>
actor = 'xtreak'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2018-12-30.15:37:18.396>
creator = 'xtreak'
dependencies = []
files = []
hgrepos = []
issue_num = 35618
keywords = []
message_count = 2.0
messages = ['332752', '338744']
nosy_count = 4.0
nosy_names = ['orsenthil', 'alex', 'serhiy.storchaka', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue35618'
versions = ['Python 3.8']