Add support for more image format?

[PontusTideman]

@viclafouch & @arnaudmanaranche

Hi!

Forked meme-studio today, and added image/gif in the EmptyContainer.tsx.
I can add a GIF file, add text, added unoptimized={true} inside <Image, but the export modal is static and so is the downloaded file.
Commented out the download="meme.png" in ExportModal.tsx so the file opens up in the browser and that is also static.

Any tip? ;D

Edit: Support for like apng and webp would be nice to also export, and not only png. ;D