Update laravel mix and sass loader (#5203)

package.json

@@ -12,10 +12,10 @@
     "devDependencies": {
         "axios": "^0.19",
         "cross-env": "^5.1",
-        "laravel-mix": "^4.0.7",
+        "laravel-mix": "^5.0.1",
         "lodash": "^4.17.13",
         "resolve-url-loader": "^2.3.1",
         "sass": "^1.15.2",
-        "sass-loader": "^7.1.0"
+        "sass-loader": "^8.0.0"
     }
 }