fix(css-plugin): Use generateBundle hook to prevent CSS imports from being lost

[susnux]

• Resolves NcRichContenteditable: @mention item is not rendered properly in other apps nextcloud-vue#4901

We must use generateBundle as Vite removes "empty css chunks" (chunks that only import css) in its generateBundle hook and merged the importedCss property down to the really emitted chunks.
Otherwise we will loose CSS imports!

See this example of the NcMentionBubble on the comments tab, current master with 8.5.1 the "after" with 8.5.1 but compiled with this changes.

before	after

[codecov]

Codecov Report

Attention: 25 lines in your changes are missing coverage. Please review.

Comparison is base (38a8ed6) 81.09% compared to head (d7d3647) 80.06%.
Report is 6 commits behind head on main.

❗ Current head d7d3647 differs from pull request most recent head 0a801cc. Consider uploading reports for the commit 0a801cc to get more accurate results

Files	Patch %	Lines
lib/plugins/ImportCSS.ts	30.55%	25 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
- Coverage   81.09%   80.06%   -1.04%     
==========================================
  Files           8        8              
  Lines         582      602      +20     
  Branches       48       48              
==========================================
+ Hits          472      482      +10     
- Misses         62       72      +10     
  Partials       48       48              

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[Antreesy]

Got the general reference for skipped css chunks at generateBundle
Please correct me, if I'm wrong with a source: https://github.com/vitejs/vite/blob/3fceb14b94b12d12d47285402980f360aa4284ea/packages/vite/src/node/plugins/css.ts#L861-L863

Also tested with apps, config does its job 🎉

[skjnldsv]

🐘