[API Feature request] Allow a link or base64 album cover to be sent with scrobbles to the maloja api

[duckfromdiscord]

My idea is to add an optional parameter to /newscrobble called cover_art which can be a base64 encoded PNG of the cover art a song is using. The reason I think this could be super useful would be if we could get it added to Web Scrobbler and have Bandcamp album covers be auto-added so that we do not need to go in and manually add cover art to every Bandcamp song. For backwards compatibility, let's just make it optional so that any API request not including it passes through. As a bonus, if we can also get FoxxMD/multi-scrobbler to support it, we won't need to deal with two separate Spotify API connections.

Of course, this would depend on #239 getting fixed. I'm still adding art to a song, the request returning as 200 OK, then I refresh the page and it's still the automatically generated random art.

I'm willing to try to open a PR for this if you're OK with that. I'm very busy IRL right now but I can maybe do this in my dwindling spare time.

[duckfromdiscord]

I don't know if I mentioned this but I spoke to the Web Scrobbler dev and the scrobble code has access to the album cover. So it should be super easy to add this on their end, I could even do a PR. The main reason I wanted this was for Web Scrobbler anyway since you can't use Spotify's metadata for a lot of the sites it supports.