Update styles to fit modern rules.

[FrenjaminBanklin]

See #2104.

Relies on #2108.

The update to Stylelint version 15 introduced a whole slew of new expectations that the existing code does not meet without significant configuration changes. Rather than overhaul (probably) every .scss file in the entire project, I opted instead to make any necessary package changes and simply override any rules that the existing code no longer passes.

Ideally rather than ignoring numerous Stylelint rules, we should update our code to validate against them where reasonably possible. This would likely mean removing most if not all of the new rule configuration changes (minus the class/id/keyframe naming rules, probably) and continuously linting the code to find rule violations, then fixing those violations and re-linting ad nauseum until everything has been modernized.

This would obviously also require checking that nothing changes in appearance following whatever changes are made.