title: Module not found: Error: Can't resolve 'core-js/es6'
body: <p>I've got a problem with my build process in relation to my React app.</p>
  
  <p>I always get the following error:</p>
  
  <p><strong>Module not found: Error: Can't resolve 'core-js/es6'</strong></p>
  
  <p>if I use this in a polyfill.js:</p>
  
  <p><strong>import 'core-js/es6';</strong></p>
  
  <p>That is my package.json:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>{
    "name": "test",
    "version": "1.0.0",
    "main": "index.js",
    "license": "MIT",
    "private": true,
    "devDependencies": {
      "@babel/core": "^7.4.0",
      "@babel/preset-env": "^7.4.2",
      "@babel/preset-react": "^7.0.0",
      "@babel/runtime": "^7.4.2",
      "babel-loader": "^8.0.5",
      "babel-preset-es2015": "^6.24.1",
      "copy-webpack-plugin": "^5.0.2",
      "css-hot-loader": "^1.4.4",
      "eslint": "5.15.3",
      "eslint-config-airbnb": "^17.1.0",
      "eslint-loader": "^2.1.2",
      "eslint-plugin-import": "2.16.0",
      "eslint-plugin-jsx-a11y": "6.2.1",
      "eslint-plugin-react": "7.12.4",
      "file-loader": "^3.0.1",
      "node-sass": "^4.11.0",
      "prettier": "^1.16.4",
      "react-hot-loader": "4.8.0",
      "sass-loader": "^7.1.0",
      "webpack": "^4.29.6",
      "webpack-cli": "^3.3.0",
      "webpack-dev-server": "^3.2.1"
    },
    "dependencies": {
      "axios": "^0.18.0",
      "core-js": "^3.0.0",
      "prop-types": "^15.7.2",
      "react": "^16.8.5",
      "react-dom": "^16.8.5",
      "react-redux": "^6.0.1",
      "react-string-replace": "^0.4.1",
      "redux": "^4.0.1",
      "slick-carousel": "^1.8.1"
    },
    "scripts": {
      "dev": "webpack-dev-server --hot",
      "build": "webpack --colors --profile --progress --env.mode production",
      "lint": "eslint ./src/ --ext .js,.jsx"
    }
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>Can someone help here?</p>