docs: Update "Describing a View" for v10 functional components

The "Getting Started > Describing a View" guide is a new user's first introduction to building a UI in Neo.mjs. It is critically outdated as it only shows the classic, class-based component model.

This ticket is to update the document to lead with the modern, functional approach introduced in v10.

Tasks

• Add a new, prominent section at the top titled "The Modern Approach: Functional Components".
• This new section should feature a code example of a simple view built with defineComponent and createVdom.
• Reframe the existing content as "The Classic Approach: Class-Based Components".
• Add a brief explanation of when to choose one approach over the other (e.g., functional for simple views, class-based for extending the component library or complex stateful logic).