fix(pack): alias donesn't work for style file

[fireairforce]

Summary

upstream pr: utooland/next.js#107

修复如下 case:

utoopack 的 alias 对于样式文件不生效:

{
  "config": {
      "resolve": {
          "alias": {
            "@/*": "./input/*" 
          }
      }
   }
}

ts 代码:

import style from '@/index.less';

console.log(style);

Test Plan

添加了快照测试