Probably Flow Typed
Converts Typescript "declaration files" into Flow "library definitions".
What this is
This is an automatic converter which takes in Typescript definitions and spits out Flowtype definitions. It's a pragmatic answer to the fact that this library has over 1000 module definitions and yet this library has an order of magnitude less.
This is an automatic process: the definition formats vary and the process is lossy. However, by clearly calling out these points and allowing developers to manually touch up the output if they so wish, this converter can grant developers who use Flow a huge library of definition files they would need to hand-craft otherwise.