[SPARK-16122][DOCS] application environment rest api

## What changes were proposed in this pull request?

follow up pr of apache#16949.

## How was this patch tested?

jenkins

Author: uncleGen <[email protected]>

Closes apache#17033 from uncleGen/doc-restapi-environment.

Author: uncleGen

docs/monitoring.md

@@ -381,6 +381,10 @@ can be identified by their `[attempt-id]`. In the API listed below, when running
   <tr>
     <td><code>/applications/[app-id]/streaming/batches/[batch-id]/operations/[outputOp-id]</code></td>
     <td>Details of the given operation and given batch.</td>
+  </tr>
+  <tr>
+    <td><code>/applications/[app-id]/environment</code></td>
+    <td>Environment details of the given application.</td>
   </tr>       
 </table>