Add doc about missing metadata headers automatically sent to kafka pubsub consumer

[passuied]

What content needs to be created or modified?
The Apache Kafka Pubsub doc is missing some details about message metadata headers automatically sent to consumer

Describe the solution you'd like
Add a section specifying which headers are passed and an example how to consume them

Where should the new material be placed?
https://github.com/dapr/docs/blob/v1.14/daprdocs/content/en/reference/components-reference/supported-pubsub/setup-apache-kafka.md

The associated pull request from dapr/dapr, dapr/components-contrib, or other Dapr code repos
N/A

Additional context
This has been available since at least v1.13