title: Use Tweenmax from cdn with webpack
body: <p>I'm loading TweenMax from cdnjs and using the <code>externals</code> option of webpack, however, I'm unable to make this work in my vue webpack setup. I'm getting <code>TweenMax is not defined</code></p>
  
  <p><img src="https://user-images.githubusercontent.com/5490862/64491341-4f093e80-d285-11e9-90f3-612f3a89b7cf.jpg" alt="Untitled-1"></p>
  
  <p>Loading script</p>
  
  <p><code>wp_enqueue_script( 'tweenmax', 'https://cdnjs.cloudflare.com/ajax/libs/gsap/2.1.3/TweenMax.min.js', array(), false, true );</code></p>
  
  <p>webpack.dev.config.js</p>
  
  <pre><code>module.exports = {
    entry: path.resolve(__dirname, 'src/app.js'),
    mode: 'development',
    devServer: {
      hot: true,
      headers: { 'Access-Control-Allow-Origin': '*' }
    },
    output: {
      path: path.resolve(__dirname, 'dist'),
      publicPath: 'http://localhost:8080/',
      filename: '[name].app.js',
      chunkFilename: '[name].app.js',
    },
    module: {
      rules: [
        {
          test: /\.vue$/,
          loader: 'vue-loader'
        },
        {
          test: /\.js$/,
          loader: "babel-loader",
          exclude: /node_modules/
        },
        {
          test: /\.css$/,
          use: [
            'vue-style-loader',
            'css-loader'
          ]
        }
      ]
    },
    plugins: [
      new VueLoaderPlugin(),
      new webpack.HotModuleReplacementPlugin(),
      new BundleAnalyzerPlugin()
    ],
    resolve: {
      alias: {
        '@': path.resolve(__dirname, './src')
      },
      extensions: ['*', '.js', '.vue', '.json']
    },
    externals: {
      jquery: 'jQuery',
      TweenMax: 'TweenMax',
    }
  }
  </code></pre>
  
  <p>.vue file</p>
  
  <pre><code>import TweenMax from 'TweenMax'
  
  $(el).each(function(i){
          TweenMax.from($(this), time, {
            opacity: 0,
            x: 0,
            y: that.random(-200, 200),
            z: that.random(500, 1000),
            // scale: .1,
            delay: i * delay,
            yoyo: true,
            repeat: -1,
            repeatDelay: time * 10,
            ease: Power1.easeOut
          });
        });
  
  </code></pre>