Use Dart Sass, instead of deprecated Node Sass. (PP-691)

[tdilauro]

Description

Replaces the Node Sass dev dependency with Dart Sass.

Motivation and Context

Node Sass is not yet supported on Apple Silicon Macs, at least not with Node 18.

Also, LibSass and packages that depend upon it, like Node Sass, are now deprecated.

• https://sass-lang.com/blog/libsass-is-deprecated/

[Jira PP-691]

How Has This Been Tested?

• Manually tested on both Intel and Apple Silicon Macs and was able to perform the following:
  • npm install
  • npm run dev-server -- ... and interact with the specified backend (used the fix in Fix webpack dev-server handling of relative URLs. (PP-690) #11 to get the dev-server working for this).
  • All npm test tests pass.
• CI passed for this feature branch.

Checklist:

• I have updated the documentation accordingly.
• All new and existing tests passed.

[ray-lee]

Looks good.