Update changelog (#1960)

changelog.txt

@@ -1,3 +1,17 @@
+4.17.0
+============
+
+New Features:
+
+**Addition of an enum TokenSource to indicate the source of a token** which can be cache, identity provider or broker. [Issue for details](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/1728)
+
+Bug Fixes:
+
+**Fix for CryptographicException when using CNG certificate**. Added support for .net classic 4.6.1. [Issue for details](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/1726)
+**Fix for ArgumentNullException thrown by MsalExtensionException constructor**. [Issue for details](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/1947)
+**Reduce response time for GetDeviceId**. MSAL now will disable MATS telemetry if it is not configured. [Issue for details](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/1912)
+**Fix for System.Net.HttpListenerException when system browser flow is cancelled**. [Issue for details](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/1773)
+
 4.16.1
 ============