Add option to delete cover file after embedding

[shayded-exe]

If I'm embedding the cover, 99% of the time I don't need the cover.jpg file.

The app should either delete it by default when embedding with an option to keep the cover, or vice-versa, offer an option to delete the cover after embedding.

Also, thank you so much for making this. You're awesome. It's really well designed, better than most CLI tools like this.