code: function sourceMaps(devtool = 'cheap-module-eval-source-map') {
    return (context, util) => {
      context.sourceMaps = true
  
      return util.merge({ devtool })
    }
  }
docs: Just a convenience wrapper to enable sourcemaps in an easier-to-read fashion
  than `setDevTool()`.
  @TODO: Only sets the javascript sourcemaps now. Would be nice to make loaders
  enable their specific sourcemaps when `sourceMaps()` is used.
  
  @param {string} [devtool]
  @return {Function}