feat: support Docs Hub Dark Mode

[henryh0x1]

Problem

Docs Hub (https://dev.jan.ai/docs/) working well in the light mode, but having an issue with dark mode. It should be configured dark mode based on style of other current docs pages.

Current Preview in Dark Mode

Success Criteria
A clear and concise description of what you want to happen.

Docs Hub should be display well in dark mode. https://dev.jan.ai/docs/

Additional context
Add any other context or screenshots about the feature request here.