[docs] Scaffold new docs theme

[aarongarciah]

https://deploy-preview-4369--base-ui.netlify.app/docs-theme

• Font weight doesn't work with our currently loaded Die Grotesk font files.
• Söhne Mono is not loaded.
• Shadows in dark mode are fully transparent.
• Dark mode colors were generated by Codex based on the light ones. Probably not quite right.
• Font sizes and line heights from (website) are included in the scales.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4369
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4369
  

commit: b9e0b8b

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[mui-bot]

Bundle size report

Bundle	Parsed size	Gzip size
@base-ui/react	0B(0.00%)	0B(0.00%)

Details of bundle changes

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✅ Deploy Preview for base-ui ready!

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[colmtuite]

• Only need two weights
• Do you wanna do space-24, space-28 naming? 😅