title: webpack split js files, get one more files
body: <p>when I use webpack 4 to split js files, then i get the dist directory contains: app.js, vendor.js and one more js file names vendor~app.js, how and why it comes? </p>
  
  <p>Here are those files:</p>
  
  <p><a href="https://i.stack.imgur.com/cKyY3.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cKyY3.jpg" alt="enter image description here"></a></p>
  
  <p>and this is my webpack config:</p>
  
  <pre><code>const path = require('path');
  
  const CleanWebpackPlugin = require('clean-webpack-plugin');
  
  module.exports = {
  
      mode: 'production',
  
      entry: {
          vendor: ['react', 'react-dom', 'redux', 'react-redux', 'react-router-dom'],
          app: './src/entry.js'
      },
  
      output: {
          path: path.resolve(__dirname, 'dist'),
          chunkFilename: '[name].js',
          publicPath: '/',
          filename: '[name].js'
      },
  
      module: {
          rules: [
              {
                  test: /\.js[x]?$/,
                  exclude: /node_modules/,
                  include: path.resolve(__dirname, 'src'),
                  use: [{
                      loader: 'babel-loader',
                      options: {
                          cacheDirectory: true,
                          babelrc: false,
                          presets: [['@babel/preset-env', {
                              "modules": false
                          }], '@babel/preset-react'],
                          plugins: ['@babel/plugin-transform-runtime', "@babel/plugin-proposal-class-properties"]
                      }
                  }]
              },
          ]
      },
  
      optimization: {
          runtimeChunk: {
              name: 'manifest'
          },
          splitChunks: {
              minChunks: 1,
              minSize: 2,
              chunks: 'all',
              name: true,
              cacheGroups: {
                  common: {
                      test: 'vendor',
                      chunks: 'initial',
                      name: 'vendor',
                      enforce: true,
                  }
              }
          }
      },
      plugins: [
          new CleanWebpackPlugin(['dist']),
      ]
  }
  </code></pre>
  
  <p>in my entry.js:</p>
  
  <pre><code>import React, { Component } from 'react'
  
  import ReactDOM from 'react-dom'
  
  class App extends Component {
  
      constructor (props) {
          super(props);
      }
  
      render () {
          return (
              &lt;div&gt;Hello World&lt;/div&gt;
          )
      }
  }
  
  ReactDOM.render(&lt;App/&gt;, document.getElementById('app'))
  </code></pre>