Create Rollup package, for use with Rollup and Vite

[TomStrepsil]

Issue

ASOS uses Rollup for library packages. It would be nice if these could be toggled, when attached to an appropriate toggle store in a host application.

Details

To support Rollup, and hence ultimately Vite (which may be an option to supplant WebPack for application code), the system should create a sibling to the Webpack package.