feat(m): add "list links" page
The main page should list all of our links, as well as allowing us to
edit or delete them. I've also rewritten the templating system here to
work off a regex, which is a lot more comfortable and also means that
templates which aren't used can avoid being evaluated (at the cost of
making a template that is used multiple times be evaluated multiple
times - perhaps we should be memoizing here?)