question: does this plugin assume webp image exist?

Hello, does this plugin check if a webp version of the image exist or not? It's more convenient than creating the declarations automatically. There is another plugin that checks for the existence of the image ([postcss-retina-bg-img](https://github.com/alexlafroscia/postcss-retina-bg-img)).

I would love to add that feature if it doesn't exist.