vue3.0不是安装node-sass , 而是sass dart
在package.json中直接写如下内容，然后npm install即可
"devDependencies": { "@vue/cli-plugin-babel": "~4.5.15", "@vue/cli-plugin-router": "~4.5.15", "@vue/cli-plugin-vuex": "~4.5.15", "@vue/cli-service": "~4.5.15", "@vue/compiler-sfc": "^3.0.0", "sass": "^1.26.5", "sass-loader": "^8.0.2" },
