out_kafka: add support for dynamic/static headers

Author: DIFRIN

pipeline/outputs/kafka.md

@@ -17,6 +17,7 @@ Kafka output plugin allows to ingest your records into an [Apache Kafka](https:/
 | dynamic\_topic | adds unknown topics \(found in Topic\_Key\) to Topics. So in Topics only a default topic needs to be configured | Off |
 | queue\_full\_retries | Fluent Bit queues data into rdkafka library, if for some reason the underlying library cannot flush the records the queue might fills up blocking new addition of records. The `queue_full_retries` option set the number of local retries to enqueue the data. The default value is 10 times, the interval between each retry is 1 second. Setting the `queue_full_retries` value to `0` set's an unlimited number of retries. | 10 |
 | rdkafka.{property} | `{property}` can be any [librdkafka properties](https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md) |  |
+| Header | Add a HTTP header key/value pair. Multiple headers can be. If static header than use Header  key value, if the value is part of the message than use Header key <value> |  |
 
 > Setting `rdkafka.log.connection.close` to `false` and `rdkafka.request.required.acks` to 1 are examples of recommended settings of librdfkafka properties.
 
@@ -45,6 +46,7 @@ In your main configuration file append the following _Input_ & _Output_ sections
     Match       *
     Brokers     192.168.1.3:9092
     Topics      test
+    Header      test test
 ```
 
 ### Avro Support