update zurb-foundation-template package.json with new dart-sass dependency.

[Carl]

What should happen?

The site should build.

What happens instead?

The site errors out due to dependency failure.

Possible Solution

Update package.json to use dart-sass vs node-sass.

This is discussed obliquely in #12581 and #12532 but there's no active issue to update zurb-foundation-template

Test Case and/or Steps to Reproduce (for bugs)

Build a site using the zurb-foundation-template package.json

• [x ] I have read and follow the CONTRIBUTING.md document.
• [x ] There are no other issues similar to this one.
• [x ] The issue title and template are correctly filled.