Ruby Sass is End-of-Life, should no longer be used

[charlesfsl]

I setup the project locally for the first time today. When I ran bundle install, it reported that "Ruby Sass has reached end-of-life and should no longer be used."

The rest of the related output had these suggestions:

• If you use Sass as a command-line tool, we recommend using Dart Sass, the new
  primary implementation: https://sass-lang.com/install

• If you use Sass as a plug-in for a Ruby web framework, we recommend using the
  sassc gem: https://github.com/sass/sassc-ruby#readme

• For more details, please refer to the Sass blog:
  https://sass-lang.com/blog/posts/7828841