title: Moment is not defined when using React with Webpack
body: <p>I'm in the progress of "Reactifying" a PHP application and am adding a single component to start (with several child components). In addition to the custom components, there are several library dependencies (react-bootstrap, moment, etc).</p>
  
  <p>I'm using webpack to compile it and it compiles correctly and generates the <code>dist/main.js</code> as expected. <strong>However, when adding it to the HTML template I get the error "moment is not defined"</strong>, though the "react-bootstrap" dependencies appear to load correctly. Based on the guidance in <a href="https://github.com/palantir/blueprint/issues/959" rel="nofollow noreferrer">https://github.com/palantir/blueprint/issues/959</a>, I tried both <code>import * as moment from 'moment'</code>, <code>import moment from 'moment'</code> as well as the <code>const moment = require('moment');</code> I had previously been using which compiled fine with browserify.</p>
  
  <p><em>webpack.config.js</em></p>
  
  <pre><code>const path = require('path')
  
  module.exports = {
      mode: 'development',
      context: path.resolve(__dirname, 'components'),
      entry: './dir/EntryComponent.app.jsx',
      resolve: {
          extensions: ['.jsx', '.json', '.js']
      },
      optimization: {
          minimize: false
      },
      module: {
          rules: [
              {
                  test: /\.(js|jsx)$/,
                  exclude: /node_modules/,
                  use: {
                      loader: 'babel-loader'
                  }
              }
          ]
      }
  };
  </code></pre>
  
  <p><em>.babelrc</em></p>
  
  <pre><code>{
    "presets": ["@babel/preset-env", "@babel/preset-react"]
  }
  </code></pre>
  
  <p><em>Component.jsx</em></p>
  
  <pre><code>import Collapse from "react-bootstrap/Collapse";
  import moment from 'moment';
  const Datetime = require('react-datetime');
  ...
  &lt;label&gt;Start&lt;/label&gt;
  &lt;Datetime
     value={this.props.startDate}
     placeholder="Start Date"
     dateFormat='YYYY-MM-DD'
     timeFormat={false}
     input={true}
     viewDate={moment().subtract(1, 'month')}
     onChange={date =&gt; this.props.updateStartDate(date)}
     closeOnSelect={true}
     closeOnTab={true}
     viewMode="months"
     inputProps={{readonly: 'readonly'}}/&gt;
  </code></pre>