Add support for Common Shake Plugin for Webpack to optimize CommonJS dependencies.

[swernerx]

There is a pretty new Webpack plugin to apply some tree shaking to classic CommonJS modules. As this does not seem to have negative side-effects we should try out whether this improves bundle sizes in production.

Plugin: https://github.com/indutny/webpack-common-shake

[artisin]

There has been some progress on this front with Webpack 4 as well as support for complex selector sideEffects.