[WCM] Encore updates for Webpack 4#10322

Merged

weaverryan merged 7 commits intosymfony:3.4from

weaverryan:encore-webpack4

Nov 5, 2018

Commits on Oct 26, 2018

documenting the new split chunks and Twig helper functions for Encore
weaverryan
committed
Adding docs for runtime.js and fixed a few other things
weaverryan
committed

Commits on Nov 5, 2018

adding a small entry about ajax code splitting
weaverryan
committed