Allowing webpack-cli v5

Hey packagers!

This release allows webpack-cli version 5 to be used in your package.json file.

Upgrading

Run:

npm install "@symfony/webpack-encore@^4.2.0" --save-dev

Or:

yarn upgrade "@symfony/webpack-encore@^4.2.0"

Changes: v4.1.2..v4.2.0

Happy Packing!