Technically yes! The DLCs from itch are independent rpa files that work on both the Steam and itch versions. You just have to download the free base game on Steam, and then move the DLC rpa files into the "game" folder of the Steam directory. You can find this by right clicking on the game in your library, clicking "Manage", and then "Browse Local Files". If you need more help getting it set up, just let me know!