Document wildcard for network interfaces
With this commit we mention how Elasticsearch behaves when
either `0` or `0.0.0.0` is used for `network.host`.
@@ -24,7 +24,9 @@ host to other nodes in the cluster. Accepts an IP address, hostname, a
<<network-interface-values,special value>>, or an array of any combination of
these. Note that any values containing a `:` (e.g., an IPv6 address or
containing one of the <<network-interface-values,special value>>) must be quoted
-because `:` is a special character in YAML.
+because `:` is a special character in YAML. `0.0.0.0` is an acceptable IP address
+and will bind to all network interfaces. The value `0` has the same effect as the
+value `0.0.0.0`.
+
Defaults to `_local_`.
