Clarify worker-count warning and note Uvicorn comparison

[ilovefreesw]

Granian currently warns when configured workers exceed CPU cores, which can confuse users who follow Uvicorn’s common heuristic (workers = 2 × cores + 1) for I/O-bound apps. Please clarify the startup warning to explain the trade-off (CPU-bound vs I/O-bound workloads) and mention the Uvicorn-style recommendation as an alternative for I/O-heavy/async servers, or link to a short doc with guidance.

Example from my app:

==> Starting arq worker...
==> Starting granian (9 workers based on 4 CPU cores)...
==> p2 running at http://localhost:8787 — Ctrl+C to stop
[WARNING] Configured number of workers appears to be higher than the amount of CPU cores available. Mind that such value might actually decrease the overall throughput of the server. Consider using 4 workers and tune threads configuration instead

[gi0baro]

Please check the readme

Also, you should generally avoid to configure workers and threads based on numbers suggested for other servers, as Granian architecture is quite different from projects like Gunicorn or Uvicorn.

[ilovefreesw]

Okay thanks. I switched back to uvicorn as I was getting more performant results that way.