On some instances of lighttpd, like the one that comes with PiHole, the
alias module is not loaded by default. This makes the configuration of
PiAware's lighttpd not work (see e.g.
https://discourse.pi-hole.net/t/pi-hole-and-piaware-lighttpd/9611).
This way we ensure that the alias module is loaded even on non-default
lighttpd configurations.