Problem: No event is triggered before creating a window.
(Sergey Vlasov)
Solution: Add the WinNewPre event (Sergey Vlasov)
fixes: vim/vim#10635closes: vim/vim#127611f47db75fd
Not sure if this should be triggered before creating a floating window,
as its use case is related to window layout.
Co-authored-by: Sergey Vlasov <sergey@vlasov.me>