Add change history entry and enclose in collapsible section

Author: mikekistler

azure/Guidelines.md

@@ -11,9 +11,13 @@ Please ensure that you add an anchor tag to any new guidelines that you add and
 
 ## History
 
+<details>
+  <summary>Expand change history</summary>
+  
 | Date        | Notes                                                          |
 | ----------- | -------------------------------------------------------------- |
-| 2022-Sep-07 | Updated URL guidelines for DNS Done Right                      |                 |
+| 2023-Apr-07 | Update/clarify guidelines on polymorphism                      |
+| 2022-Sep-07 | Updated URL guidelines for DNS Done Right                      |
 | 2022-Jul-15 | Update guidance on long-running operations                     |
 | 2022-May-11 | Drop guidance on version discovery                             |
 | 2022-Mar-29 | Add guidelines about using durations                           |
@@ -24,6 +28,8 @@ Please ensure that you add an anchor tag to any new guidelines that you add and
 | 2020-Jul-31 | Added service advice for initial versions                      |
 | 2020-Mar-31 | 1st public release of the Azure REST API Guidelines            |
 
+</details>
+
 ## Introduction
 
 These guidelines apply to Azure service teams implementing _data plane_ APIs. They offer prescriptive guidance that Azure service teams MUST follow ensuring that customers have a great experience by designing APIs meeting these goals: