fix: DHCP and DNS input rule for guest zone (#143)

Add input rule for dns and dhcp services from the guest zone

zones_and_policies.rst

@@ -66,6 +66,9 @@ To create a Guest zone, follow these steps:
 - select ``Drop`` for both ``Traffic to firewall`` and ``Traffic for the same zone`` fields
 - click on the ``Save`` button and apply the changes
 
+.. note::
+  If the firewall is intended to provide ``DHCP`` and ``DNS`` services, create a firewall ``input rule`` allowing traffic on ports ``53 TCP/UDP (DNS)`` as well port ``67 UDP (DHCP)`` for the ``Guest`` zone.
+  If these services are not required or provided by another device in this network, the corresponding ports can remain blocked.
 
 DMZ zone (orange)
 ^^^^^^^^^^^^^^^^^