I’d like to buy the game, but I’d prefer to wait to buy it on Steam, unless you plan to give a key to everyone who already paid for it here. I’ve only seen a little bit of gameplay, and it looks like a fantastic game!
If you’d like to, you can set it up on itch.io so that everyone that pays for the game gets access to a Steam key. From what I understand, this also allows anyone who has previously paid for the game to claim a Steam key.
You can find more details here: Download keys - External keys