Old dependency on del causes errors on Windows

[Manfred Brands]

Issue description or question

You depend on del version 4.1.1, in the mean time there is del version 6.0.0
The old version has some issues deleting directories.

When I manually update yarn.lock to pretend clean-webpack-plugin depends on del version 6.0.0, the webpack serve command runs successfully.

webpack serve output:

```bash
<i> [webpack-dev-server] Project is running at:
<i> [webpack-dev-server] Loopback: http://localhost:3001/
<i> [webpack-dev-server] On Your Network (IPv4): http://10.1.1.64:3001/
<i> [webpack-dev-server] Content not from webpack is served from 'C:\Development\Fugro\fugro.utilization.service.aws\spa\lib' directory
<i> [webpack-dev-middleware] wait until bundle finished: /
<e> [webpack-dev-middleware] Error: ENOTEMPTY: directory not empty, rmdir 'C:\Development\Fugro\fugro.utilization.service.aws\spa\lib\assets'
<e>     at Object.rmdirSync (fs.js:890:10)
<e>     at rmkidsSync (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\del\node_modules\rimraf\rimraf.js:364:25)
<e>     at rmdirSync (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\del\node_modules\rimraf\rimraf.js:342:7)
<e>     at Function.rimrafSync [as sync] (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\del\node_modules\rimraf\rimraf.js:312:9)
<e>     at C:\Development\Fugro\fugro.utilization.service.aws\node_modules\del\index.js:65:11
<e>     at Array.map (<anonymous>)
<e>     at module.exports.sync (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\del\index.js:57:40)
<e>     at CleanWebpackPlugin.removeFiles (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\clean-webpack-plugin\dist\clean-webpack-plugin.js:179:37)
<e>     at CleanWebpackPlugin.handleInitial (C:\Development\Fugro\fugro.utilization.service.aws\node_modules\clean-webpack-plugin\dist\clean-webpack-plugin.js:119:10)
<e>     at C:\Development\Fugro\fugro.utilization.service.aws\node_modules\clean-webpack-plugin\dist\clean-webpack-plugin.js:84:14 {
<e>   errno: -4051,
<e>   syscall: 'rmdir',
<e>   code: 'ENOTEMPTY',
<e>   path: 'C:\\Development\\Fugro\\fugro.utilization.service.aws\\spa\\lib\\assets'
<e> }

Webpack Config

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CopyPlugin = require("copy-webpack-plugin");
const { CleanWebpackPlugin } = require('clean-webpack-plugin');
var webpack = require('webpack');

module.exports = {
  //  mode: 'none',
    entry: {
        app: path.join(__dirname, 'src', 'index.tsx')
    },
    target: 'web',
    resolve: {
        extensions: ['.ts', '.tsx', '.js']
    },
    devServer: {
        static: [
            {
                directory: path.resolve(__dirname, 'lib'),
                watch: true
            }
        ],
        compress: true,
        port: 3001,
        open: true
    },
    module: {
        rules: [
            {
                test: /\.tsx?$/,
                use: 'ts-loader',
                exclude: '/node_modules/'
            },
            {
                test: /\.css$/i,
                use: ['style-loader', 'css-loader'],
            },
            {
                test: /\.(png|jpe?g|gif)$/i,
                use: [
                    {
                        loader: 'file-loader'
                    },
                ],
            },
        ],
    },
    output: {
        filename: '[name].[contenthash].js',
        path: path.resolve(__dirname, 'lib'),
        clean: true
    },
    plugins: [
        new CleanWebpackPlugin(),
        new HtmlWebpackPlugin({
            template: path.join(__dirname, 'src', 'index.html')
        }),
        new webpack.ProvidePlugin({
            process: 'process/browser',
        }),
    ]
}

Environment

  System:
    OS: Windows 10 10.0.18363
    CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
    Memory: 17.57 GB / 31.77 GB
  Binaries:
    Node: 14.15.4 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 6.14.10 - C:\Program Files\nodejs\npm.CMD