Automating webp in Jekyll

So, we have a plugin which appears to trawl through a folder of images and output webp versions. I see in the config you can opt to replace the existing extension (png, jpg etc.) or append webp to it (resulting in a filename like image.jpg.webp). Second option sounds best as it will avoid having to do some string manipulation with the filename in the figure and image includes (i.e. replace jpg with webp). Assuming the first build will be the most painful as hopefully it checks for an existing webp file before creating a new one. Let’s see.