Update changelog (#12612)

* Update changelog

Author: azabbasi

sdk/digitaltwins/Azure.DigitalTwins.Core/CHANGELOG.md

@@ -1,5 +1,13 @@
 # Release History
 
+## 1.0.0-preview.2
+
+### New features
+
+- Official public preview of [Azure.DigitalTwins.Core SDK](https://www.nuget.org/packages/Azure.DigitalTwins.Core)
+- [Azure Digital Twins Public Repo](https://github.com/Azure/azure-sdk-for-net/tree/master/sdk/digitaltwins/Azure.DigitalTwins.Core)
+- [Azure Digital Twins Samples](https://github.com/Azure/azure-sdk-for-net/tree/master/sdk/digitaltwins/Azure.DigitalTwins.Core/samples)
+
 ## 1.0.0-preview.1 (Unreleased)
 
 ### New features
@@ -17,6 +25,3 @@
 ### Fixes and improvements
 
 - N/A
-
-## 1.0.0-preview.2
-