Update dependency sass to v1.88.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
sass	1.86.3 -> 1.88.0

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Release Notes

sass/dart-sass (sass)

v1.88.0

Compare Source

• Allow custom properties with empty values (such as --var:;).

• Fix a bug when calculating source spans for interpolations.

Dart and JS APIs

• Potentially breaking bug fix: Throw an error when passing a function or
  mixin object from one compilation to another.

Dart API

• Deprecate passing a relative URL to compileString() and related functions.

v1.87.0

Compare Source

• Potentially breaking bug fix: When a plain CSS file with a top-level
  nesting selector & is loaded into a nested Sass context via
  meta.load-css() or @import, Sass now emits plain CSS nesting rather than
  incorrectly combining it with the parent selector using a descendant
  combinator.

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