Simplify Webpack configuration

[sapegin]

Something like this:

webpackConfig: {
  resolve: {
    extensions: ['.scss'],
  },
  module: {
    loaders: [
      {
        test: /\.jsx?$/,
        include: [dir],
        loaders: ['babel'],
      },
      {
        test: /\.scss$/,
        include: [dir],
        loaders: ['style', 'css', 'sass?precision=10'],
      },
    ],
  },
  postcss: () => ([
    autoprefixer,
  ]),
},

Or:

webpackConfig: env => { /* ... */ },

Also easier to reuse project’s config:

const _ = require('lodash');
const webpackConfig = require('webpack.config.js');
module.exports = {
  title: 'React Style Guide Example',
  components: 'lib/components/**/[A-Z]*.js',
  webpackConfig: _.pick(webpackConfig, ['resolve', 'module', 'postcss']),
};

With the current updateWebpackConfig option it’s too easy to accidentally overwrite options required for Styleguidist itself and spend a lot of time debugging (like #214).