Adds a workshop addon for the client to download before entering the server.

Having the raw files from a workshop item does not count as having already downloaded it.
So players who previously downloaded a map through Fast Download will have to re-download it if you use the workshop.

You should try to only add addons that have custom content ( models, sounds, etc ).

Gamemodes that are workshop enabled are automatically added to this list - so there's no need to add them.

The server's current map is also automatically added, if it is loaded from a workshop addon.