Move www. redirect to GH Pages

[Dan-Q]

Previously when I pointed www.freedeedpoll.org.uk at GH Pages, GH stopped generating TLS certs (like: at all). So right now a different server does the www to non-www redirection. It'd be nice to move it all to GH Pages. Ideally, starting with dropping the TTL really low so it can be reverted if it makes a mess again.

Worth waiting until all the search engines have solidly got the hang of the non-www URL first.