[Feature Request] Download series cover art from plugin when downloading a manga

[melyux]

Is your feature request related to a problem? Please describe.
Seems like Mango doesn't grab a series cover art from the plugin. It downloads the cover art during the plugin search, but it doesn't seem to actually save these images when downloading the chapter and creating the series. You can still set the cover art manually though.

Describe the solution you'd like
When downloading a Manga, Mango should save the series cover art image locally from the plugin and populate the "cover art" field initially with it.

Describe a small use-case for this feature request
The Home and Library views would show the actual series art instead of showing the series' first chapters' cover arts.

Additional context
I may have missed something in the code, or this could be a plugin-only problem (though I don't think so).