Fix: Replace deprecated node-sass with sass

Node Sass is considered deprecated - the recommended alternative is Dart Sass.
This change implements the suggested migration, as outlined at the following
URL:
https://sass-lang.com/blog/libsass-is-deprecated#how-do-i-migrate

pinry-spa/package.json

@@ -26,7 +26,7 @@
     "babel-eslint": "^10.0.3",
     "eslint": "^5.16.0",
     "eslint-plugin-vue": "^5.0.0",
-    "node-sass": "^4.13.1",
+    "sass": "^1.37.5",
     "sass-loader": "^8.0.0",
     "vue-template-compiler": "^2.6.10"
   }