CSS minification not handling / relative paths to _node_modules_

[thescientist13]

For example, referencing something like PrismJS CSS in an inline <style> tag is not getting optimized

For example

<style>
    @import url('/node_modules/prismjs/themes/prism-twilight.css');
</style>

Comes out without any minification applied

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Seems like we'll just need to make an exception in our @import handling logic.