My two cents: _don't_ mention your game in their chat!
Streamers take what they do seriously (as they should), and I don't think they want games advertised publicly on their chat while they're streaming a different game. If you want to let them know about your game, I think it would be a better idea to first PM them a question about if they're okay with you telling them about a game rather than just launching into an advert. So instead of "Hey, here's a link to a game I think you'd like," you could say something like "I enjoyed watching you stream <game name> today! I'm working on a similar game. Would you like to hear about it?" And then, unless they say (explicitly) "yes" I wouldn't contact them any further. Again, though, this is just my two cents.