[SDP] PipelinesHandler visually

Author: jaceklaskowski

docs/declarative-pipelines/PipelinesHandler.md

@@ -2,7 +2,9 @@
 
 `PipelinesHandler` is used to [handle pipeline commands](#handlePipelinesCommand) in [Spark Connect]({{ book.spark_connect }}) ([SparkConnectPlanner]({{ book.spark_connect }}/server/SparkConnectPlanner), precisely).
 
-`PipelinesHandler` acts as a bridge between Python and SQL "frontends" and Spark Connect Server (where pipeline execution happens).
+`PipelinesHandler` acts as a bridge between Python execution environment of [Spark Declarative Pipelines](index.md) and [Spark Connect Server]({{ book.spark_connect }}/server/) (where pipeline execution happens).
+
+![PipelinesHandler](./images/spark-sql-sdp-PipelinesHandler.png)
 
 ## Handle Pipelines Command { #handlePipelinesCommand }