fix: replace problematic sass-node dependency (deprecated) with sass

[malek-aktir]

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Short description of what this resolves:

Many issues have been reported in regards to npm install failure due to sass-node dependency: #2102 #2056 #1467.

sass-node seems to require the presence of python2 (not big deal), but also a specific version .NET SDK on windows plateforms (couple of gigabytes), and even with that it still fails randomly for various reasons.

this depedency is deprecated anyway, and sass (dart-based implementation) is recommanded as drop-in replacement which is also compatble with sass-node.

A discussion about this topic on reddit :
https://www.reddit.com/r/node/comments/ey82ov/its_2020_why_is_nodegyp_still_breaking_builds/