Fix deprecation warning with Sass 1.77.7

[julien-deramond]

Warning

This PR is a draft probably tackling only a part of the problem

Warning

#474 (comment) has not been tested out as it might be another issue

Closes #474

Description

This PR is an attempt to fix #474.

Context

git checkout main
npm i sass@1.77.7
npm run test

Deprecation Warning: Sass's behavior for declarations that appear after nested
rules will be changing to match the behavior specified by CSS in an upcoming
version. To keep the existing behavior, move the declaration above the nested
rule. To opt into the new behavior, wrap the declaration in `& {}`.

More info: https://sass-lang.com/d/mixed-decls

    ╷
153 │ ┌     .enable-rfs &,
154 │ │     &.enable-rfs {
155 │ │       @content;
156 │ │     }
    │ └─── nested rule
... │
299 │           #{$property}: if($rfs-mode == max-media-query, $fluid-val, $val);
    │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ declaration
    ╵
    scss.scss 299:9            @content
    scss.scss 167:7            -rfs-media-query-rule()
    scss.scss 298:7            rfs()
    test/sass/_main.scss 38:5  @import
    test/sass/test-4.scss 2:9  root stylesheet

Warning: 18 repetitive deprecation warnings omitted.

The issue comes from our internal mixins _rfs-rule and _rfs-media-query-rule that can both render @content; without any selector; that causes for instance this kind of rules:

@content;

.enable-rfs &,
&.enable-rfs {
   @content;
}

@content;

Since there are supposed to be internal mixins, I supposed that I could modify them without any problems for users, and chose to only extract the problematic rule from _rfs-media-query-rule, and use it before calling _rfs-rule:

@if $rfs-class == enable {
    @if $rfs-mode == min-media-query {
      @content;
    }
}

Maybe there's a smarter way of doing it, but I'm not that familiar with this repo.