alfred: optionally bundle a lua script for generating a bat-hosts

Provide a lua script that uses alfred to propagate and collect all
interface mac + names, then generate a /tmp/bat-hosts file.
If there's already a (probably hand-made) /etc/bat-hosts it won't overwrite it,
but if there's none, it will symlink /etc/bat-hosts -> /tmp/bat-hosts

Signed-off-by: Gui Iribarren <gui@altermundi.net>
Thanks-to: Joshua Head <joshua.head@outlook.com>