title: Error: Cannot find module 'stylelint' Webpack
body: <p>I tried to include a scss linter to my webpack config file.
  But every time I run "npm run start" my console print this error message:</p>
  
  <p><strong>Error: Cannot find module 'stylelint'</strong></p>
  
  <p>The plugin is installed and my webpack.config.dev.js looks like this:</p>
  
  <pre><code>const merge = require('webpack-merge')
  const webpack = require('webpack')
  const common = require('./webpack.config.common')
  const user = require('./scripts/utils/format-config')(require('./main.config.js'))
  var styleLintPlugin = require('stylelint-webpack-plugin');
  
  const cssLoaders = (
    [
      {
        loader: 'style-loader',
        options: {
          sourceMap: true,
          singleton: true // avoid CSS Flashing
        }
      }
    ].concat(common.CSSLoaders)
  )
  
  // append resolve-url-loader before the preprocessor loader so that
  // we can avoid broken relative url with the dev server
  if (user.css.preprocessorLoader) {
    for (let i = 0; i &lt; cssLoaders.length; i++) {
      const obj = cssLoaders[i]
      if (obj.loader !== user.css.preprocessorLoader) continue
      cssLoaders.splice(i, 0,
        {
          loader: 'resolve-url-loader',
          options: { sourceMap: true }
        }
      )
      break
    }
  }
  
  const devConfig = {
    mode: 'development',
    entry: user.entries,
    module: {
      rules: [
        {
          test: user.css.sourceRegexExt,
          use: cssLoaders
        },
        {
          test: /\.(svg|png|jpg|gif|ttf|otf|woff|woff2|eot)$/,
          use: [
            {
              loader: 'file-loader',
              options: {}
            }
          ]
        }
      ]
    },
    plugins: [
      new webpack.NoEmitOnErrorsPlugin(),
      new webpack.NamedModulesPlugin(),
      new webpack.HotModuleReplacementPlugin(),
      new styleLintPlugin({
        configFile: '.stylelintrc',
        context: 'src',
        files: '**/*.scss',
        failOnError: false,
        quiet: false,
        syntax: 'scss',
      }),
    ],
    devtool: '#eval-source-map'
  }
  
  module.exports = merge(common.webpack, devConfig)
  </code></pre>
  
  <p>I would be happy for every answer =)I would be happy for every answer =)</p>