The update is very massive, which pack new features, fixes and others.
The main feature of the update is the “Kaiju scale”, which allows you to scale the size of the environment of the game. This update also adds companion eye-cam (switching the companion-camera to follow your eyes around). Other additions include new way of rating contraptions (by giving a smooth to favorite them), Neko Modding, more languages (Japanese), new avatar and hats and Twitch Avatar Voting and more.
Check out the link at the end of this blog post to access the full details of the change log.