Move from node-sass to sass

.gitlab-ci.yml

-image: node:12
+image: node:12-alpine
 stages:
   - test
   - build

package.json

@@ -50,8 +50,8 @@
     "lodash-webpack-plugin": "^0.11.5",
     "mini-css-extract-plugin": "^0.5.0",
     "mocha": "^7.1.1",
-    "node-sass": "^4.14.1",
     "optimize-css-assets-webpack-plugin": "^5.0.3",
+    "sass": "^1.26.10",
     "sass-loader": "^7.3.1",
     "vue-loader": "^15.9.1",
     "vue-template-compiler": "^2.6.11",