Modernize Sass import rules by using `@use` and `@forward`

[bmunkholm]

Problem

make html produced a bunch of deprecation warnings.

WARNING in ./src/crate/theme/rtd/crate/static/vendor/furo/styles/furo.sass (./node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[0].use[1]!./node_modules/postcss-loader/dist/cjs.js??ruleSet[1].rules[0].use[2]!./node_modules/sass-loader/dist/cjs.js??ruleSet[1].rules[0].use[3]!./src/crate/theme/rtd/crate/static/vendor/furo/styles/furo.sass)
Module Warning (from ./node_modules/sass-loader/dist/cjs.js):
Deprecation Warning on line 2, column 8 of file:///Users/bmunkholm/code/c/docs/crate-docs-theme/src/crate/theme/rtd/crate/static/vendor/furo/styles/furo.sass:2:8:

Evaluation

Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.

More info and automated migrator: https://sass-lang.com/d/import
2 | https://github.com/import "variables"

Poke

An attempt to fix that was done in #657 but reverted again in #672 due to #668.

Next

It would be nice to figure out how to get rid of those warnings properly as it hides "real" warnings as we get used to ignore warnings when building.

[amotl]

Recap

In general, we should follow what Furo is doing. About this specific case, is that upstream note of any relevance to this topic?

Sass has deprecated @import, something that Furo relies on fairly heavily.

• Deal with the consequences of https://sass-lang.com/d/import pradyunsg/furo#858

Status

It looks like GH-657 by @bmunkholm already tried to resolve the problem by using @use rules, but something went south.