Add a CHANGELOG entry for mbullington/node_preamble.dart#6
Add a CHANGELOG entry for mbullington/node_preamble.dart#6

This doesn't actually require any changes in Dart Sass itself, but it
was producing behavior that was visible to our users (#301) so it
makes sense to include it in the CHANGELOG for the version that will
include the fix.

[skip ci]

sass/dart-sass,sass/dart-sass