Fixing bug with copyFiles()

Hi Webpackers!

This release fixes a bug that was introduced with Encore 1.0 and Webpack 5 related to copyFiles(). See #894 for the details.

The fix was done in #930 - a big thanks to @Lyrkan.

To upgrade:

yarn upgrade "@symfony/webpack-encore@^1.1.1"

Changes: https://github.com/symfony/webpack-encore/compare/v1.1.0..v1.1.1

Documentation: http://symfony.com/doc/current/frontend.html

Happy packing!