[pkg] add changelog

CHANGELOG

+0.21.6
+======
+
+- A new and shiny gateway selector!
+- Allow to select obfs4 gateways (bridges)
+- Ability to define explicit allowed addresses for local networks.
+

docs/firewall.rst

+firewall
+========
+
+If you want to explicitely define allowed ips in private ranges, please use the files::
+
+  /etc/bitmask/ipv4.allow
+  /etc/bitmask/ipv6.allow
+
+With one ip per line.