title: "Support for the experimental syntax 'decorators-legacy' isn't currently enabled" error
body: <p>I'm using mobx in a react app and I keep getting this error: <code>Support for the experimental syntax 'decorators-legacy' isn't currently enabled</code> in the title even though I tried <a href="https://stackoverflow.com/questions/52262084/syntax-error-support-for-the-experimental-syntax-decorators-legacy-isnt-cur/53746840#53746840">this</a> solution, deleted <code>node_modules</code> folder and <code>npm install</code>-ed, here are my files:</p>
  
  <pre><code>// .babelrc
  
  {
    "presets": ["@babel/preset-env"],
    "plugins": [
      ["@babel/plugin-proposal-decorators", { "legacy": true }],
      ["@babel/plugin-proposal-class-properties", { "loose": true }]
    ]
  }
  
  // package.json
  
  {
    "name": "app-spotify",
    "version": "0.1.0",
    "private": true,
    "dependencies": {
      "@testing-library/jest-dom": "^4.2.4",
      "@testing-library/react": "^9.5.0",
      "@testing-library/user-event": "^7.2.1",
      "axios": "^0.19.2",
      "mobx": "^5.15.4",
      "mobx-react": "^6.1.8",
      "react": "^16.13.0",
      "react-dom": "^16.13.0",
      "react-router-dom": "^5.1.2",
      "react-scripts": "3.4.0"
    },
    "scripts": {
      "start": "react-scripts start",
      "build": "react-scripts build",
      "test": "react-scripts test",
      "eject": "react-scripts eject"
    },
    "eslintConfig": {
      "extends": "react-app"
    },
    "browserslist": {
      "production": [
        "&gt;0.2%",
        "not dead",
        "not op_mini all"
      ],
      "development": [
        "last 1 chrome version",
        "last 1 firefox version",
        "last 1 safari version"
      ]
    },
    "devDependencies": {
      "@babel/core": "^7.1.0",
      "@babel/plugin-proposal-class-properties": "^7.1.0",
      "@babel/plugin-proposal-decorators": "^7.1.0",
      "@babel/preset-env": "^7.1.0"
    }
  }
  </code></pre>