Includes using the subtheme namespace do not work in storybook.

Problem/Motivation

Creating a new component in a subtheme that references another SDC component in the subtheme namespace will not correctly render when viewed in the storybook.

Proposed resolution

This occurs because the sdc-plugin that storybook uses to resolve a namespace and component name to the include files only works for the `civictheme` namespace. Adding the ability to configure the supported namespaces in vite.config.js will allow components referencing namespaces other than civictheme to correctly render as well.