LibWeb: Implement 'connection timing info' struct

Author: https://github.com/linusg
Commit: 1f8ed8fca7
Pull-request: https://github.com/SerenityOS/serenity/pull/15795
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/davidot ✅

Userland/Libraries/LibWeb/Forward.h

@@ -192,6 +192,7 @@ class Response;
 namespace Web::Fetch::Infrastructure {
 class Body;
 struct BodyWithType;
+class ConnectionTimingInfo;
 struct Header;
 class HeaderList;
 class Request;