bug/issue 1355 handle CSS import attributes with PostCSS plugin when prerendering

[thescientist13]

Related Issue

resolves #1355

Documentation

N / A

Summary of Changes

1. Don't extension check in PostCSS plugin intercepting lifestyle per - https://github.com/ProjectEvergreen/www.greenwoodjs.dev/pull/153/files#diff-745fdda9fef5a58b2eebf6f4a4ccfffa2506fcfb7c2722295528c375bfe71681R432
2. Have PostCSS plugin forward incoming response.headers

TODO

1. logo FOUC now? - just needed to refine the implementation
2. Downstream testing
3. other instances of extension check in intercepting
   • CSS Modules - N / A
   • Babel - enhancement/avoid extension checking in Babel resource plugin intercept lifecycle #1366
4. (own issue) should the contents / results be inlined or externalized (currently being inlined)? - supported Import Attributes from node modules are not being externalized based on polyfill configuration settings #1365
   • Seems like it should be externalized but we only check for local files - https://github.com/ProjectEvergreen/greenwood/blob/v0.31.0-alpha.1/packages/cli/src/config/rollup.config.js#L34
   • should we also be doing more mergeResponse in rollup.config.js? Had to formally pass response.headers here from PostCSS plugin, but maybe this was intentional for this specific use case?
5. split off Babel plugin work into its own PR - enhancement/avoid extension checking in Babel resource plugin intercept lifecycle #1366