Add <string> and <string_view> includes to C++ toast snippet

Agent-Logs-Url: https://github.com/MicrosoftDocs/windows-dev-docs-pr/sessions/87cac495-2ca3-44a8-ab34-6456b329d67c

Co-authored-by: GrantMeStrength <[email protected]>

Author: Copilot

hub/apps/desktop/modernize/desktop-to-uwp-enhance.md

@@ -148,6 +148,8 @@ void ShowToast(string title, string content, string image, string logo)
 
 ```cppwinrt
 #include <sstream>
+#include <string>
+#include <string_view>
 #include <winrt/Windows.Data.Xml.Dom.h>
 #include <winrt/Windows.UI.Notifications.h>