doc: example of include usage in configuration file

doc/reference.rst

@@ -78,6 +78,91 @@ Matching files are processed in sorted order.
 
  include: STR
 
+File include example
+--------------------
+
+*knot.conf*::
+
+ include: log.conf
+
+ server:
+     rundir: "/var/run/knot"
+     user: knot:knot
+     listen: [ 127.0.0.1@53, ::1@53 ]
+
+ database:
+     storage: "/var/lib/knot"
+
+ template:
+   - id: default
+     storage: "/var/lib/knot"
+     file: "%s.zone"
+
+ zone:
+   - domain: example.com
+
+*log.conf*::
+
+ log:
+   - target: syslog
+     any: info 
+
+Pattern include example
+-----------------------
+
+*knot.conf*::
+
+ include: conf/*.conf
+
+ server:
+     rundir: "/var/run/knot"
+     user: knot:knot
+     listen: [ 127.0.0.1@53, ::1@53 ]
+
+ log:
+   - target: syslog
+     any: info 
+
+ database:
+     storage: "/var/lib/knot"
+
+ template:
+   - id: default
+     storage: "/var/lib/knot"
+     file: "%s.zone"
+
+*conf/primary.conf*::
+
+ remote:
+   - id: secondary
+     address: 192.168.1.1@53
+
+ acl:
+   - id: acl_secondary
+     address: 192.168.1.1
+     action: transfer
+
+ zone:
+   - domain: example.com
+     notify: secondary
+     acl: acl_secondary
+
+*conf/secondary.conf*::
+
+ remote:
+   - id: primary
+     address: 192.168.2.1@53
+
+ acl:
+   - id: acl_primary
+     address: 192.168.2.1
+     action: notify
+
+ zone:
+   - domain: example.net
+     master: primary
+     acl: acl_primary
+
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 Module section