SSR usage and implementation details

The readme says the plugin is SSR Friendly, but I was wondering if you could give some more details about that.

Is there anything I would need to do to configure a project to use this plugin with SSR?

I would expect that things like `document.createElement` would fail on the server since the DOM isn't available to provide `document`:

https://github.com/faceyspacey/extract-css-chunks-webpack-plugin/blob/c6402525a08b8b34cf2de8893ed2789808726d59/src/index.js#L354

Is there another code path that gets run on the server?

I have tried looking through past issues for more details, but haven't been able to find out more yet.

Start with the README's SSR Friendly claim and inspect src/index.js around line 354, especially the document.createElement reference. Trace which code path runs during server-side rendering and identify any required project configuration; update the SSR documentation with the confirmed behavior and setup details.

Written by the indexing model from the issue text.