treeherder/babel.config.json

{
  "presets": [
    [
      "@babel/preset-env",
      {
        "debug": false,
        "useBuiltIns": false,
        "targets": {
          "browsers": [
            "last 1 Chrome versions",
            "last 1 Edge versions",
            "last 1 Firefox versions",
            "last 1 Safari versions"
          ]
        }
      }
    ],
    [
      "@babel/preset-react",
      {
        "development": true,
        "useSpread": true
      }
    ]
  ],
  "plugins": [
    "@babel/plugin-syntax-dynamic-import",
    "react-hot-loader/babel",
    [
      "@babel/plugin-proposal-class-properties",
      {
        "loose": true
      }
    ]
  ]
}