Warn users when configuring auto upload for nested folders to prevent duplicate file syncing

In my opinion it isn't clear enough that some of the folders in Settings -> Auto Upload can be synced while being apart of another folder that is already being synced.

You have to specifically go into the configure menu to see the path of the directory you're trying to sync, otherwise you might not know. This became a problem for me when I was syncing files and wondering why there was a duplicate of every file in the "Screenshots" directory.

I would propose that Nextcloud warn you when you're about to sync a folder that's inside another one or about to sync a folder that is going to sync a folder you already have synced.