title: Webpack cannot resolve core-js paths on Windows
body: <p>Running webpack I receive the errors:</p>
  <pre><code>ERROR in ./node_modules/core-js/index.js
  Module not found: Error: Can't resolve './es' in 'pathtoproject\node_modules\core-js'
   @ ./node_modules/core-js/index.js 1:0-15
   @ multi core-js whatwg-fetch ./src/contactForm.tsx
  
  ERROR in ./node_modules/core-js/index.js
  Module not found: Error: Can't resolve './internals/path' in 'pathtoproject\node_modules\core-js'
   @ ./node_modules/core-js/index.js 4:11-38
   @ multi core-js whatwg-fetch ./src/contactForm.tsx
  
  ERROR in ./node_modules/core-js/index.js
  Module not found: Error: Can't resolve './proposals' in 'pathtoproject\node_modules\core-js'
   @ ./node_modules/core-js/index.js 2:0-22
   @ multi core-js whatwg-fetch ./src/contactForm.tsx
  
  ERROR in ./node_modules/core-js/index.js
  Module not found: Error: Can't resolve './web' in 'pathtoproject\node_modules\core-js'
   @ ./node_modules/core-js/index.js 3:0-16
   @ multi core-js whatwg-fetch ./src/contactForm.tsx
  
  </code></pre>
  <p>The folders do exist though. I believe it's to do with Windows paths as when I change the core-js/index.js file to use path.resolve() instead of relative imports it does work. This is not the solution I want though as it requires altering the core-js module.</p>
  <p>For reference here is my <strong>webpack.config.js</strong></p>
  <pre><code>const path = require('path');
  
  module.exports = {
      entry: [&quot;core-js&quot;, &quot;whatwg-fetch&quot;, &quot;./src/contactForm.tsx&quot;],
  
      output: {
          path: path.join(__dirname, &quot;build/assets/js/&quot;),
          filename: &quot;contactForm.js&quot;
      },
  
      mode: &quot;production&quot;,
  
      // Enable sourcemaps for debugging webpack's output.
      devtool: &quot;source-map&quot;,
  
      resolve: {
          // Add '.ts' and '.tsx' as resolvable extensions.
          extensions: [&quot;.ts&quot;, &quot;.tsx&quot;]
      },
  
      module: {
          rules: [
              {
                  test: /\.ts(x?)$/,
                  exclude: /node_modules/,
                  use: [
                      {
                          loader: &quot;ts-loader&quot;
                      }
                  ]
              },
              // All output '.js' files will have any sourcemaps re-processed by 'source-map-loader'.
              {
                  enforce: &quot;pre&quot;,
                  test: /\.js$/,
                  loader: &quot;source-map-loader&quot;
              }
          ]
      },
  
      // When importing a module whose path matches one of the following, just
      // assume a corresponding global variable exists and use that instead.
      // This is important because it allows us to avoid bundling all of our
      // dependencies, which allows browsers to cache those libraries between builds.
      externals: {
          &quot;react&quot;: &quot;React&quot;,
          &quot;react-dom&quot;: &quot;ReactDOM&quot;
      }
  };
  
  </code></pre>
  <p>Any ideas of a fix would be greatly appreciated</p>