[SPARK-16438] Add Asynchronous Actions documentation

## What changes were proposed in this pull request?

Add Asynchronous Actions documentation inside action of programming guide

## How was this patch tested?

check the documentation indentation and formatting with md preview.

Author: sandy <phalodi@gmail.com>

Closes #14104 from phalodi/SPARK-16438.

docs/programming-guide.md

@@ -1101,6 +1101,9 @@ for details.
 </tr>
 </table>
 
+The Spark RDD API also exposes asynchronous versions of some actions, like `foreachAsync` for `foreach`, which immediately return a `FutureAction` to the caller instead of blocking on completion of the action. This can be used to manage or wait for the asynchronous execution of the action.
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 ### Shuffle operations
 
 Certain operations within Spark trigger an event known as the shuffle. The shuffle is Spark's