Is there some notification addon?

Hmm, I don't know of any, but https://www.steamgifts.com/giveaways/search?type=wishlist will show them. Perhaps you already know about that, though... :)

no. this site was made to have people interacting with each other, not to be a store that gives away games.
you can filter giveaways by type in the sidebar

View attached image.

I feel like you've already asked that in the past and people already told you there wasn't one.

Edit: Well, at least I was right about the first part. X