Bug 32978: Replace node-sass with dart-sass

Bug 32978: Replace node-sass with dart-sass

'npm install' fails in ktd on aarch64, giving unsupported architecture error for node-sass.

This patch addresses this by replacing node-sass with dart-sass, updating our gulpfile
accordingly. Some corrections have been made to SCSS to fix warnings
raised during the build process.

Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>
Works like a charm. Great work oleonard! Tested on Apple M1, e.g. aarch64.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Edit: I removed some useless formatting changes in the gulpfile, and the
yarn.lock changes as well.
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>