Link .NET Foundation Code of Conduct (#257)

.github/CODE_OF_CONDUCT.md

@@ -1,3 +1,6 @@
 # Code of Conduct
 
-This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
+This project has adopted the code of conduct defined by the Contributor Covenant
+to clarify expected behavior in our community.
+
+For more information, see the [.NET Foundation Code of Conduct](https://dotnetfoundation.org/code-of-conduct).