Webpack5的变化

1. 开箱即用webpack serve命令，只需要安装webpack-dev-server就可以直接启用了。

Usage: webpack s | serve
Description: Run the webpack Dev Server

此时，npx webpack-dev-server命令会报错，因此它只兼容Webpack4，不过Webpack5可以使用它：

Cannot find module ‘webpack-cli/bin/config-yargs‘
Require stack:
- C:\Users\ly\Desktop\TypeScript\node_modules\webpack-dev-server\bin\webpack-dev-server.js