add background color based on the OS mode (#7117)
* add background color based on the OS mode
* add changeset
* use static css instead
* format
* changes
* changes
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Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>
Co-authored-by: Abubakar Abid <abubakar@huggingface.co>
Co-authored-by: pngwn <hello@pngwn.io>
Co-authored-by: Ali Abid <aliabid@Alis-MacBook-Pro.local>
