Merge pull request #292823 from jowang-msft/jowang-msft/acscallingdotnetsdk1

Add ACS Calling SDK .NET entry

Author: v-ccolin

articles/communication-services/toc.yml

@@ -1348,6 +1348,8 @@ items:
       href: https://azure.github.io/azure-sdk-for-android/azure-communication-calling/index.html
     - name: Calling (iOS)
       href: /objectivec/communication-services/calling/
+    - name: Calling (.NET)
+      href: /dotnet/api/azure-communication-services/calling/
   - name: Call Automation
     items:
     - name: Call Automation (JavaScript)