Make banner work when re-loaded

[ibobo]

My project use next-intl for internationalization, and I had to move my layout.tsx inside a [locale] folder. This is fine in most situation, but when navigating between languages, some cookie dependent features stopped working.

When the current locale is changed, since che layout is inside the [locale] folder, all providers are unmounted and mounted again and it turns out that when this is done to the IubendaProvider it doesn't work anymore since it loses its internal state.

This PR fixes this issue by checking if the Iubenda scripts are already loaded when the provider is mounted, updating then its internal state with data from the _iub object without waiting for the callback, which isn't called at all in this situation.

[liarco]

Hi @ibobo,
thank you for your valuable feedback and for this PR. Will make sure to review this as soon as possible and also to include it into a new release if doesn't introduce any breaking changes.

@ivanbalmita let's talk about this later today to check if we can speed this up in any ways. Thx.