ElementUI 按需引入坑爹的点记录

官网说的是这样的：

但实际上，应该是这样修改：

{
  "presets": [
    ["env", {
      "targets": {
        "browsers": ["> 1%", "last 2 versions", "not ie <= 8"]
      }
    }],
    "stage-2"
  ],
  "plugins": [
      "transform-vue-jsx", 
      "transform-runtime",
      ["component", {
          "libraryName": "element-ui",
        "styleLibraryName": "theme-chalk"
      }]
   ]
}