Support webp images

I would like to suggest that we do this in a different way, so that other modules could alter image style warmup with their own event and/or alter hook, because these other modules better knows how to handle own calls and code.

Otherwise we always have to check if something of code structure was changed in these used modules.

For this I referenced another issue with this one.

Adding the correct tag got Drupal Global Contribution Weekend 2023.

Thanks for the quick fix patch in #5.