Inject a file into the main compilation

plugin.js

module.exports.apply = function(compiler) {
  var SingleEntryPlugin = require ('webpack/lib/SingleEntryPlugin');

  var styleguideName = 'atrium-styleguide-core';
  var styleguideEntry = 'atrium-entry.js';
  var styleguideFileName = 'atrium/core.js';

  // Inject entry into the main compilation
  compiler.apply(new SingleEntryPlugin(
      this.context, 
      __dirname + '/' + styleguideEntry,
      styleguideName
  ));

  // Output configuration of the injected entry
  compiler.plugin('compilation', function(compilation) {
    compilation
        .mainTemplate
        .plugin('asset-path', function(name, data) {
          return (data.chunk && data.chunk.name === styleguideName) ? styleguideFileName : name;
        });
  });
    
}