Enhaning Cover Support for base automation

[ghero101]

I would like to suggest that Komga, look inside the folder of a given series for a file called "cover" or something similar, which your variety of image formats, and then use that as the Cover for the series as a default. This would aid in managing the covers of the media. Additionally it should be set in a way that if the user manually provides a new cover that it doesnt get overwritten on the next file scan.

[gotson]

This already exists: https://komga.org/docs/guides/local-artwork-assets