Add to Plex watchlist instead of Radarr/Sonarr

[LeendertPlas]

I would like the items missing from collections to be able to be added to the plex watchlist instead of Radarr/Sonarr.

This seems to be supported by the PlexAPI through (https://python-plexapi.readthedocs.io/en/latest/modules/myplex.html#plexapi.myplex.MyPlexAccount.addToWatchlist)

It seems to be like this would be a small addition, as the missing items are already listed and should easily be able to be added via a different method, but i don't know how i would call this in the existing functions.