Converted image is downloaded with incorrect extension when using redirects

[lubieowoce]

Version: 0.17.3 Configuration: HTTP redirect to existing webp Additional details: multisite install Description: Redirects work great for displaying in the browser -- foo.jpg is correctly redirected to foo.jpg.webp. However, when the user does *right-click* > Save Image, it is incorrectly saved as foo.jpg despite actually being a WebP file.

I don't know much about browser behavior re: filenames; I'm guessing that by default it's based on the URL. But AFAIK we can override that with something like:

Content-Disposition: attachment; filename="foo.jpg.webp"