README suggestion: add a quicker first-time evaluation path

[YANGCHUNHONG3000]

Hi! I came across llm-d Router and liked how clearly the README explains the router/EPP architecture.

One small docs suggestion: the README is technically strong, but the top section is very dense for a first-time visitor. A new reader has to process terminology changes, API consolidation notes, architecture, modes, and links before they get a simple “how do I try this?” path.

A few quick wins that might improve the first 30 seconds:

1. Add a short “Who this is for” block near the top

   • Example: platform teams running LLM inference on Kubernetes who need load-aware / prefix-cache-aware routing.

2. Add a small “Quick evaluation path” before the deep architecture sections

   • prerequisites
   • minimal standalone setup
   • expected first successful request / signal
   • link to full architecture docs afterward

3. Move the terminology/API change notices under a “Project status / migration notes” section

   • They are important, but putting both before the main pitch makes the opening feel heavier than it needs to be.

Possible top structure:

# llm-d Router
One sentence: what it does, who it is for, and why it matters.

## Who this is for
## Quick evaluation path
## Architecture at a glance
## Modes of operation
## Core components and APIs
## Project status / migration notes
## Contributing

No pressure — just a README/onboarding suggestion. The project is complex enough that a slightly clearer top-level reader journey could help new users evaluate it faster.