Prevent double encoding of pagedown option object literal

[jberger]

If Mojolicious adds a encode_json_text, then it really should be used here https://github.com/jberger/Galileo/blob/master/lib/Galileo/Page.pm#L42

otherwise something like

helper javascript_literal => sub { Mojo::Util::decode 'UTF-8', encode_json(pop) }

would work too bug involve an unnecessary encoding round-trip