Language selector pop-up?

Hi,

In a multilanguage website, what would be the best way of implementing a pop-up window that asks the user which language they want to visit the site?

For instance, when you’re visiting zalando.de from a Spanish IP (or with a browser with Spanish as main language), zalando asks you if you really want to browse their German site or if you’d rather visit zalando.es. This is done through a dialogue / modal.

I was wondering if Grav or any plugin offers this mechanism, and, if they don’t, what would be a way to implement it.

TIA

Marco