Changelog: 🚀

## Breaking changes

### Drop webpack 3 support

Webpack 3 is no longer supported, webpack 4 is the minimum required version.

As a side effect you shouldn’t see any webpack warnings when you run Styleguidist.

We’ve also replaced no longer maintainer uglify-es with Terser to minify production JavaScript bundle.

* #1175, #1178 by @derz
* #1165 by @elevatebart
* #1148 by @elevatebart
* #915, #1023 by @stepancar
* #1180 by @AndreyGladkov

Author: Artem Sapegin