[Velocity]The development section may need to add an event usage prompt

[pingguomc]

Now, we know that PreLoginEvent cannot obtain the UUID of players in offline mode, but there are still many developers who are unclear about this matter, leading to frequent questions on forums and issues.

Perhaps we need to add some hints in the document.

Perhaps you can add it in /velocity/dev/pitfalls/ , or in /velocity/dev/event-api/.

Thanks for you.