Add links to the mailinglist subscription and arhive on the presentation page

[adiroiban]

Right now there is just a link to a wiki page https://twistedmatrix.com/trac/wiki/TwistedCommunity#MailLists

and the wiki page has dead links as the wiki was not updated after the migration... I have upgraded now.

So I guess that on the new page, we only need 2 links:

• subscribe - https://mail.python.org/mailman3/lists/twisted.python.org/
• archives - https://mail.python.org/archives/list/twisted@python.org/