bundleconfig.json was removed from the 2.1 templates because it relied on a tool not created or supported by Microsoft. See https://github.com/aspnet/templating/issues/326.
This file [bundleconfig.json] is for configuring the various incantations of the BundlerMinifier tool, which isn’t actually shipped in the templates, or supported by Microsoft.
The ASP.NET Core team has replaced bundleconfig with “libman”. Rightclick the project –> Add –> Client Side Library and add the packages you need