Sass Upgrade - Stylelint

[rfultz]

Summary

Let's get back to linting & checking our scss formatting.

We currently aren't doing either.

Notes/considerations

Prettier is awfully opinionated—enough that we've intentionally removed it.

Stylelint has excellent support and we can use the same configuration with npm, CLI, and IDE.

Completion criteria

• A scss linter and format checker/reporter has been added to our workflow.
• The team has decided and implemented some rules
• npm scripts include command(s) to lint / format and auto-fix our scss files
• IDEs (at least VS Code; Sublime would be nice) are using the linting and formatting rules defined in the repo
• Tech-debt ticket(s) created to follow up and scoot us toward supporting rules we're currently skipping
• Ticket created to include scss linter/formatter in build scripts -OR- that work is included here

[rfultz]

Closing this and moving the updated work to #6387