Laravel Mix 6 support

[sebastiandedeyne]

This branch correctly compiles the test stylesheet, but there are a few more (I believe upstream) issues that need to be resolved before this is stable.

• Webpack throws an error that postcss-loader is missing, despite it being installed and available in node_modules. Adding postcss-loader as an explicit dependency solves the issue
• Some plugins require Postcss 7, others 8. These are generally compatible with each other, so it's just the upstream packages that need to change their required Postcss versions to 8. This can be solved if you're using yarn by adding a resolutions entry in your package.json.

Once the stylesheets builds without these workarounds, this can be merged. Either way, I'm waiting on a stable Laravel Mix 6 release to tag this one.

[adamwathan]

Fix is to install postcss in the example, you need to manually install postcss most of the time now as PostCSS 8 is meant to be used as a peerDependency 👍

From postcss-loader docs:

[thecrypticace]

The latest Laravel Mix v6 beta now installs PostCSS 8 if it's not installed in the root package.json file. The postcss-loader error also disappeared after moving PostCSS to a peer dependency in Mix.

[sebastiandedeyne]

Released!