d/control: recommends nftables in the iptables-nftables-compat package

So, users can use nft to check what the migrated ruleset looks like.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>

debian/control

@@ -43,6 +43,7 @@ Package: iptables-nftables-compat
 Architecture: linux-any
 Priority: optional
 Depends: ${misc:Depends}, ${shlibs:Depends}, libxtables10 (=${binary:Version})
+Recommends: nftables
 Description: iptables compat tools for nftables
  this package includes the compat tools to load iptables, ip6tables, arptables
  and ebtables rules to the nf_tables kernel subsystem.