Separate out initial sass structure

[rfearing]

The initial sass structure is based on the design system starter, created by Philip Zastrow as a way to kick-off our sass that aligns to our sass coding standards

In a perfect world:

• Sass Starter lives in its own repo and pulled in on the initial creation of a SparkPress project.
• It lives behind some sort of flag or an environment variable (See Create a flag (or some sort of setting) that allows a developer to opt-out of sass starter)