Update DeploymentGuide.md

add new section

Author: Atulku-Microsoft

documents/DeploymentGuide.md

@@ -137,6 +137,13 @@ Depending on your subscription quota and capacity, you can [adjust quota setting
 
 **⚠️ Warning:** Insufficient quota can cause deployment errors. Please ensure you have the recommended capacity or request additional capacity before deploying this solution.
 
+</details>
+<details>
+
+  <summary><b>Reusing an Existing Log Analytics Workspace</b></summary>
+
+  Guide to get your [Existing Workspace ID](/documents/re-use-log-analytics.md)
+
 </details>
 
 ### Deploying with AZD