Announcing Partial & Required Flow utility types + catch annotations

:::info[Historical] This post announced Partial, Required, and catch annotations when it was introduced. For current syntax and behavior, see the Utility Types documentation. :::

Starting in Flow version 0.201, make an object type’s fields all optional using Partial<ObjType> (use instead of the unsafe $Shape), and make an object type’s optional fields required with Required<ObjType>.