Switch to using Dart Sass to build CSS

package.json is required for building the module's CSS so it cannot be removed.
The lock file technically could be removed and added to .gitignore though as the dependency tree is entirely handled by node-sass and updates to packages would be handled by upstream if I understand how npm works.

node-sass is abandoned and the recommended replacement is Dart Sass so as part of addressing old vulnerable code this issue will encompass that change.

Automatically closed - issue fixed for 2 weeks with no activity.