Docs: Improve visibility/integration of design system docs [UXR]

[josmperez]

Incorporate feedback such as:

• Wasn’t aware of Design System documentation, didn’t connect these docs to UI components.
• Had difficulties trying to understand how to use the UI components. They had to spend time playing with the components, not too familiar with React.
• Suggests better beginner docs on Grafana-specific UI components, such as tutorials. No tutorials available.
• Wants a link to components on the Getting Started page.