Add a CI test.sh covering both firewall variants. It verifies the daemon
binary links and prints its usage banner, that the procd init script, UCI
config and iface hotplug files are installed, and that the variant-specific
firewall assets ship: fw3 include for iptables, nft fragments for nftables.
It also drives the config-file parser, which runs before firewall setup,
with an invalid and a valid config to confirm both paths behave.
Signed-off-by: Alexandru Ardelean <alex@shruggie.ro>
