This PR is a major change to Sass compilation in Discourse.
The new version of sass-ruby moves to dart-sass putting we back on the supported version of Sass. It does so while keeping compatibility with the existing method signatures, so minimal change is needed in Discourse for this change.
This moves us
From:
- sassc 2.0.1 (Feb 2019)
- libsass 3.5.2 (May 2018)
To:
- dart-sass 1.58
This update applies the following breaking changes:
>
> These breaking changes are coming soon or have recently been released:
>
> [Functions are stricter about which units they allow](https://sass-lang.com/documentation/breaking-changes/function-units) beginning in Dart Sass 1.32.0.
>
> [Selectors with invalid combinators are invalid](https://sass-lang.com/documentation/breaking-changes/bogus-combinators) beginning in Dart Sass 1.54.0.
>
> [/ is changing from a division operation to a list separator](https://sass-lang.com/documentation/breaking-changes/slash-div) beginning in Dart Sass 1.33.0.
>
> [Parsing the special syntax of @-moz-document will be invalid](https://sass-lang.com/documentation/breaking-changes/moz-document) beginning in Dart Sass 1.7.2.
>
> [Compound selectors could not be extended](https://sass-lang.com/documentation/breaking-changes/extend-compound) in Dart Sass 1.0.0 and Ruby Sass 4.0.0.
SCSS files have been migrated automatically using `sass-migrator division app/assets/stylesheets/**/*.scss`
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