The VTI World Kit is the VRChat-side component of VRChat Twitch Integration (For Worlds!). It consists of numerous scripts and prefabs in order to enable the VTI Companion App to communicate with the VRChat World. The VTI spec is also rather flexible, and is set up to allow for easy extensibility for world creators looking to make their own custom events.
Purchase the VTI World Kit: https://stevegreendesign.com/project/vti/