adapt webpack example for visjs-network

[micahstubbs]

adapt the webpack example from the vis.js README for visjs-network. inspired by #57

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Example 3: Integrate vis.js components directly in your webpack build

You can integrate e.g. the timeline component directly in you webpack build.
Therefor you can e.g. import the component-files from root direcory (starting with "index-").

TODO: add analogous Network example

import { DataSet, Network } from 'vis/index-timeline-graph2d'

var container = document.getElementById('visualization')
var data = new DataSet()
var timeline = new Network(container, data, {})

To get this to work you'll need to add some babel-loader-setting to your webpack-config:

module: {
  module: {
    rules: [{
      test: /node_modules[\\\/]vis[\\\/].*\.js$/,
      loader: 'babel-loader',
      query: {
        cacheDirectory: true,
        presets: [ "babel-preset-env" ].map(require.resolve),
        plugins: [
          "transform-es3-property-literals", // #2452
          "transform-es3-member-expression-literals", // #2566
          "transform-runtime" // #2566
        ]
      }
    }]
  }
}

There is also an demo-project showing the integration of vis.js using webpack.