feat: postcss config .cts support

[sapphi-red]

Description

postcss-load-config doesn't support .cts and that makes a bit harder to migrate to "type": "module".
This PR adds a patch to support .cts as a short term solution. For a long term solution, I guess postcss/postcss-load-config#249 would work.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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