Update fluentd example (oracle#1479)

* update fluentd example * updates based on review feedback

Author: markxnelson

docs-source/content/samples/simple/elastic-stack/weblogic-domain/_index.md

@@ -120,6 +120,10 @@ data:
  format11 / <(?<severity>(.*?))>/
  format12 / <(?<messageID>(.*?))>/
  format13 / <(?<message>(.*?))>/
+ # use the timestamp field in the message as the timestamp
+ # instead of the time the message was actually read 
+ time_key timestamp
+ keep_time_key true
  </parse>
  </source>
  <match **>
@@ -131,6 +135,12 @@ data:
  index_name "#{ENV['DOMAIN_UID']}"
  scheme https
  ssl_version TLSv1_2
+ key_name timestamp 
+ types timestamp:time
+ # inject the @timestamp special field (as type time) into the record
+ # so you will be able to do time based queries.
+ # not to be confused with timestamp which is of type string!!!
+ include_timestamp true
  </match>
 EOF
 ```