Upgrade webpack to version 4.

Origami as of now works on webpack version 3.10 but webpack 4 has been released which has a lot of improvements over webpack3 including less build time and better plugin architecture.
Take a look at [Webpack4 what's new](https://auth0.com/blog/webpack-4-release-what-is-new/)

Upgrading the version will improve performance and will make builds faster.

Start by locating Origami's webpack dependency, configuration, and build entry points, then compare the current setup with the linked Webpack 4 release notes. Run the existing build before making changes and verify that it still completes successfully after the upgrade with improved build performance.

Written by the indexing model from the issue text.