JPEG support in CLI

[thrnd]

For example, i have 2 exactly the same images but one in .png and other in .jpg extensions and i want to compare them.

[thrnd]

Oh, right now i'm getting Error: Invalid file signature btw.

[mourner]

No — the CLI that accompanies the library is very basic and can only compare PNGs. We might want to add JPG support though, e.g. with https://github.com/eugeneware/jpeg-js

[TacoTheDank]

Please consider adding JPEG/JPG support 👍

[lukasoppermann]

I would also love it if you could add JPEG support. It could help with this issue: americanexpress/jest-image-snapshot#209 which is important as jest tests can be a lot faster when using jpeg instead of png.