Add option to treat series as season

[Wortex17]

As there is a major split between western-centric metadata providers that organize animes into seasons and most anime focused providers that don't and often don't even have the concept of seasons, it is almost impossible to have a neat colleciton that e.g. uses anilist and tmdb at the same time.

A quick solution could be to give this plugin the option to treat a jellyfin "season" like a series / provide season metadata by actually matching a serie sin the backend - and possibly use season 1 as the template for the series metadata itself. This could also be supported by the various anime mapping projects ie https://github.com/Fribb/anime-lists

While deifnitely not the optimal solution, it would probably circumvent the hard-lock onto a set of metadata providers.

I guess that would mean , though, that there'd need to be some way to add "series id" to the season.nfo files (or rely on the mapping files mentioned above)