feat: support dark mode and revamp docs visuals

[shadowusr]

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[github-actions]

✅ Successfully deployed static

• Docs website
• Storybook

[shadowusr]

All files in src/theme come from swizzling. It's a feature that lets you eject built-in docusaurus component to modify it. You can read more here: https://docusaurus.io/docs/swizzling

Code structure was mostly kept intact, but I modified some things like icons, visuals and styles to fit with the new docs style.