Stylelint is a css linter: https://stylelint.io/
As part of this change we have added two javascript scripts:
```
pnpm lint:css
pnpm lint:css:fix
```
Look at `.vscode/settings.json.sample` and `.vscode/extensions.json` for
configuration in VSCode.
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Co-authored-by: Joffrey JAFFEUX <j.jaffeux@gmail.com>
