The layouts have been extracted to a separate package
(@tesseract-design/viewfinder) which can be found in the Modal Pack
Registry.

The landing page contains the previews for each layout.

This implements the router based on Next.js for left-sidebar-with-menu
layout.

In addition, the other layouts have been genericized for wider framework
support, although the underlying API is still based on Next.js
components.

The styling for mobile has been implemented.

Add files from create-next-app