Replace node-sass with Dart Sass (#3197)

LibSass has been deprecated. Their maintainers
[recommend](https://sass-lang.com/blog/libsass-is-deprecated) switching
to Dart Sass instead.

Author: taneliang

website/package.json

@@ -17,7 +17,7 @@
     "test:integration": "jest --config jest.integration.config.js",
     "test:watch": "jest --watch",
     "e2e": "nightwatch -e default,safariMobile,safariDesktop,edge",
-    "ci": "cross-env NODE_ENV=production yarn lint && yarn typecheck && yarn test && yarn test:integration && npm rebuild node-sass && yarn build"
+    "ci": "cross-env NODE_ENV=production yarn lint && yarn typecheck && yarn test && yarn test:integration && yarn build"
   },
   "author": "NUSModifications",
   "license": "MIT",
@@ -99,14 +99,14 @@
     "jest-junit": "12.0.0",
     "mini-css-extract-plugin": "1.3.4",
     "nightwatch": "0.9.21",
-    "node-sass": "5.0.0",
     "npm-run-all": "4.1.5",
     "postcss-loader": "4.1.0",
     "prettier": "2.2.1",
     "react-dev-utils": "11.0.1",
     "react-refresh": "0.9.0",
     "redux-logger": "3.0.6",
     "redux-mock-store": "1.5.4",
+    "sass": "1.32.5",
     "sass-loader": "10.1.1",
     "style-loader": "2.0.0",
     "stylelint": "13.8.0",