d/: include NEWS file

Give additional instructions for users installing this version of the package.
Signed-off-by: Arturo Borrero Gonzalez <arturo@debian.org>

debian/NEWS

+iptables (1.8.1-1) unstable; urgency=medium
+
+    By default, this package will try to use the nf_tables kernel backend
+    instead of the xtables one. Please, read more about this in
+    /usr/share/doc/iptables/README.Debian, including details about the new
+    update-alternatives configuration possibilities.
+    This is a major update on the way iptables works and may have severe impact
+    in running systems which are upgrading between Debian versions.
+    The arptables and ebtables binaries are also affected, and those packages
+    will be updated soon as well.
+
+ -- Arturo Borrero Gonzalez <arturo@debian.org>  Wed,  24 Oct 2018 14:00:00 +0200