We'd love to add Uplay, but it's not going be possible for now.
Ubisoft doesn't enable collections to be viewed publically. Unless you give us your login and password, we won't be able to see what games there are in your Uplay library. Obviously, we're not going to ask users for their passwords.
Hopefully in the future Ubisoft will allow users to share their collection publicly and once that happens, we will be able to add synchronization on GG.deals.