Change: switch from scss-lint to stylelint

Change pattern proposal: migrate from scss-lint to stylelint completely

Old Pattern

scss-lint is no longer actively maintained because the SCSS team switched to Dart. It does not support modern SCSS and CSS features, for instance, place-items.

New Pattern

Stylelint is actively maintained and has better and up-to-date support for latest SCSS and CSS things.

Advantages of switching patterns

1. Modern and up-to-date tool for linting SCSS.
2. Faster CI pipeline because we have two tools for linting SCSS at the moment.
3. We already have our SCSS configuration https://gitlab.com/gitlab-org/frontend/gitlab-stylelint-config.
4. We can easily implement our own rules if required.

Disadvantages of switching patterns

1. Zero?

What is the impact on our existing codebase?

1. Like I mentioned above, a faster CI pipeline.
2. Unified and one for linting SCSS.

Reference implementation

Here is the merge request with removed scss-lint: gitlab-org/gitlab!39846 (closed)