执行webpack后报错，
You may need an appropriate loader to handle this file type

看起来像是找不到合适的 loader 加载 css

webpack.config.js

var path = require('path')
const VueLoaderPlugin = require('vue-loader/lib/plugin')
module.exports = {
    entry: './src/lib/index.js',
    output: {
        path: path.join(__dirname, './dist'),
        filename: 'vue-toast-demo.js'
    },
    module: {
        rules:[
            {
                test:/\.vue$/,
                exclude:/node_modules/,
                loader: 'vue-loader',
                include:path.join(__dirname, 'src'),
                options:{
                    loaders:{
                        scss:'style-loader!css-loader!postcss-loader!sass-loader'
                    },
                    extractCSS: true
                }
            },
            {
                test:/\.js$/,
                loader:'babel-loader',
                include:path.join(__dirname,'src'),
                exclude:/node_modules/
            }
        ]
    },
    plugins:[
        new VueLoaderPlugin("index.css")
    ]
}

package.json

{
  "name": "vue-toast-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "ankkaya",
  "license": "ISC",
  "dependencies": {
    "css-loader": "^1.0.1",
    "postcss-loader": "^3.0.0",
    "style-loader": "^0.23.1",
    "vue-loader": "^15.4.2",
    "vue-style-loader": "^4.1.2",
    "vue-template-compiler": "^2.5.17",
    "webpack": "^4.26.1"
  },
  "devDependencies": {
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.5",
    "babel-preset-env": "^1.7.0",
    "node-sass": "^4.10.0",
    "sass-loader": "^7.1.0",
    "webpack-cli": "^3.1.2"
  }
}