Bump Elastic Stack to 8.18.3

- Logstash: include syslog output plugin and config example

docker/elk/logstash/dist/http_input.conf

@@ -17,5 +17,12 @@ output {
     template => "/etc/logstash/tpot-template.json"
     template_overwrite => "true"
   }
-
+  # Syslog Output Example
+  # syslog {
+  #   host => "192.168.1.1"
+  #   port => 514
+  #   protocol => tcp
+  #   appname => "logstash-logs"
+  #   severity => "6"
+  # }
 }