Implement a hiding mechanism for sticky banners

Maybe once it becomes sticky, it could shrink and show a shorter message?

I think the close button is good-enough as a solution for this TBH, because it's a more respectful way to allow users to hide banners as-and-when they wish to do so.

Originally posted by @pradyunsg in https://github.com/python/peps/issues/2992#issuecomment-1464897620

The specific UX might differ from the initial discussion referenced above, based on whether we want to completely hide the banner or just move it to a non-sticky state (avoiding a re-flow of the content on "close").

Inizia leggendo la discussione collegata in python/peps#2992, prestando particolare attenzione ai punti relativi ai pulsanti di chiusura, al ridimensionamento e all’evitare il reflow dei contenuti. Chiarisci se il banner debba essere completamente nascosto o reso non-sticky, quindi definisci l’interazione utente prevista e il comportamento di accettazione prima di individuare l’implementazione.