## What changes were proposed in this pull request?

Add Structured Streaming Kafka Source to the `examples` project so that people can run `bin/run-example StructuredKafkaWordCount ...`.

## How was this patch tested?

manually tested it.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #18101 from zsxwing/add-missing-example-dep.

(cherry picked from commit 98c38529)
Signed-off-by: Shixiong Zhu <shixiong@databricks.com>