What minimum information should the itch.io page contain when the game is submitted?

Another unrelated question, but I can’t find an English onomatopoeia that describes the sound of a whistle? In French you could have something like this: “TRIT , TRIIIIIIT , TRllll , TRRRRRRIT”.

That's entirely up to you. However, I would suggest that you put a little bit of effort into describing your game, giving instructions on how to play it and make the page look pretty. For most people that find your game, now and in the future, this page is the one where they get their first impression and decide whether or not it's worth playing your game.

Also keep in mind that you will be judged on documentation, which includes this page.

For the whistle, it's normally something like 'Tweet', or similar.