[New docs] Implement typography design changes

[tkajtoch]

Summary

The new documentation website comes with a fresh and improved typography. We need to implement the UI changes it requires.

Acceptance Criteria

• The content typography should be adjusted to match the design (link)
• The following elements' styles should be updated:
  • Document title (code)
  • Document content (code - where it's rendered, code - where markdown is converted to components)
  • Links (code)
  • Headings (code)
  • Lists (code)
• EUI components should be used instead of custom CSS whenever possible and time efficient