chore(deps): update dependency github-markdown-css to v5.7.0

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
github-markdown-css (source)	minor	5.6.1 -> 5.7.0

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Release Notes

sindresorhus/github-markdown-css (github-markdown-css)

### [`v5.7.0`](https://redirect.github.com/sindresorhus/github-markdown-css/releases/tag/v5.7.0) [Compare Source](https://redirect.github.com/sindresorhus/github-markdown-css/compare/v5.6.1...v5.7.0) - Regenerate GitHub CSS [`382e6d0`](https://redirect.github.com/sindresorhus/github-markdown-css/commit/382e6d0)

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Configuration

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