Add sass-loader dev dependency

Author: Jason Tame

package.json

@@ -15,6 +15,8 @@
     },
     "devDependencies": {
         "laravel-mix": "^6.0",
+        "node-sass": "^8.0.0",
+        "sass-loader": "^13.2.0",
         "vue-loader": "^16.8.3"
     },
     "dependencies": {