webpack 4.0 安装出现的小问题 （One CLI for webpack must be installed）

安装的webpack版本是4.11.0，运行命令npm start 提示：
One CLI for webpack must be installed. These are recommended choices, delivered as separate packages:

• webpack-cli (https://github.com/webpack/we...
  The original webpack full-featured CLI.
• webpack-command (https://github.com/webpack-co...
  A lightweight, opinionated webpack CLI.

We will use "npm" to install the CLI via "npm install -D".
Which one do you like to install (webpack-cli/webpack-command):

这个接着输入 webpack-cli 或者 webpack-command 即可