How about Documenting the Assignment of Random Ports when Specifying Port 0 in Uvicorn?

[Hiroshiba]

I am currently developing a command to launch a server with FastAPI. I've noticed that Uvicorn seems to automatically assign a random port when port 0 is chosen, but I didn't find any documentation confirming this behavior.

I believe this feature is quite handy and would benefit others. Could we consider adding a section in the documentation that explains this behavior?

[Kludex]

PR welcome. 👍