anchor.diff:    Developers typically have separate configurations for development, production, and test environments.
     All three have a lot of configuration in common.
   
  -  开发、生产、测试不同的环境通常会分开配置，但实际上这些配置也有很多地方是通用的。
  +  开发、生产、测试等不同的环境通常会分开配置，但实际上这些配置也有很多地方是通用的。
   
     Gather the common configuration in a file called `webpack.common.js`.
   
  
positive.code:     If Webpack should resolve extension-less files for styles and HTML,
      add `.css` and `.html` to the list.
  
      如果我们希望Webapck也能解释不带扩展名的样式和HTML文件，在列表里追加`.css`和`.html`即可。
  
  a#common-rules
  :marked
  
negative.code:   Tell Webpack to resolve extension-less file requests by looking for matching files with
    `.ts` extension or `.js` extension (for regular JavaScript files and pre-compiled TypeScript files).
  
    但实际上大部分`import`语句都不带扩展名，我们可以告诉Webpack，在查找这些没有扩展名的文件时，自动加上`.ts`或者`.js`扩展名来匹配。
    
  +makeExample('webpack/ts/config/webpack.common.js', 'resolve', 'config/webpack.common.js')(format=".")
  .l-sub-section
  