prescod/Type signature

## Type signature
{|+AbstractComponent: type AbstractComponent<-Config, +Instance = mixed> = React$AbstractComponent<Config, Instance>, +Children: {+count: (children: ChildrenArray<any>) => number, +forEach: <T>(children: ChildrenArray<T>, fn: (child: T, index: number) => mixed, thisArg?: mixed) => void, +map: <T, U>(children: ChildrenArray<T>, fn: (child: $NonMaybeType<T>, index: number) => U, thisArg?: mixed) => Array<$NonMaybeType<U>>, +only: <T>(children: ChildrenArray<T>) => $NonMaybeType<T>, +toArray: <T>(children: ChildrenArray<T>) => Array<$NonMaybeType<T>>}, +ChildrenArray: type ChildrenArray<+T> = $ReadOnlyArray<ChildrenArray<T>> | T, +Component: class React$Component<Props, State = void>, +ComponentType: type ComponentType<-P> = React$ComponentType<P>, +ConcurrentMode: ({children: ?React$Node}) => React$Node, +Config: type Config<Props, DefaultProps> = React$Config<Props, DefaultProps>, +Context: type Context<T> = React$Context<T>, +DOM: any, +Element: type Element<+C> = React$Element<C>, +ElementConfig: type ElementConfig<C> = React$ElementConfig<C>, +ElementProps: type ElementProps<C> = React$ElementProps<C>, +ElementRef: type ElementRef<C> = React$ElementRef<C>, +ElementType: type ElementType = React$ElementType, +Fragment: ({children: ?React$Node}) => React$Node, +Key: type Key = React$Key, +Node: type Node = React$Node, +Portal: type Portal = React$Portal, +PropTypes: ReactPropTypes, +PureComponent: class React$PureComponent<Props, State = void>, +Ref: type Ref<C> = React$Ref<C>, +StatelessFunctionalComponent: type StatelessFunctionalComponent<P> = React$StatelessFunctionalComponent<P>, +StrictMode: ({children: ?React$Node}) => React$Node, +Suspense: React$ComponentType<{children?: ?React$Node, fallback?: React$Node, maxDuration?: number}>, +checkPropTypes: <V>(propTypes: any, values: V, location: string, componentName: string, getStack: ?(() => ?string)) => void, +cloneElement: React$CloneElement, +createClass: React$CreateClass, +createContext: <T>(defaultValue: T, calculateChangedBits: ?((a: T, b: T) => number)) => React$Context<T>, +createElement: React$CreateElement, +createFactory: <ElementType: React$ElementType>(type: ElementType) => React$ElementFactory<ElementType>, +createRef: <T>() => {current: (null | T)}, +default: {|+Children: {+count: (children: ChildrenArray<any>) => number, +forEach: <T>(children: ChildrenArray<T>, fn: (child: T, index: number) => mixed, thisArg?: mixed) => void, +map: <T, U>(children: ChildrenArray<T>, fn: (child: $NonMaybeType<T>, index: number) => U, thisArg?: mixed) => Array<$NonMaybeType<U>>, +only: <T>(children: ChildrenArray<T>) => $NonMaybeType<T>, +toArray: <T>(children: ChildrenArray<T>) => Array<$NonMaybeType<T>>}, +Component: class React$Component<Props, State = void>, +ConcurrentMode: ({children: ?React$Node}) => React$Node, +DOM: any, +Fragment: ({children: ?React$Node}) => React$Node, +PropTypes: ReactPropTypes, +PureComponent: class React$PureComponent<Props, State = void>, +StrictMode: ({children: ?React$Node}) => React$Node, +Suspense: React$ComponentType<{children?: ?React$Node, fallback?: React$Node, maxDuration?: number}>, +checkPropTypes: <V>(propTypes: any, values: V, location: string, componentName: string, getStack: ?(() => ?string)) => void, +cloneElement: React$CloneElement, +createClass: React$CreateClass, +createContext: <T>(defaultValue: T, calculateChangedBits: ?((a: T, b: T) => number)) => React$Context<T>, +createElement: React$CreateElement, +createFactory: <ElementType: React$ElementType>(type: ElementType) => React$ElementFactory<ElementType>, +createRef: <T>() => {current: (null | T)}, +forwardRef: <Config, Instance>(render: (props: Config, ref: ({current: (null | Instance)} | (((null | Instance)) => mixed))) => React$Node) => React$AbstractComponent<Config, Instance>, +isValidElement: (element: any) => boolean, +lazy: <P>(component: () => Promise<{default: React$ComponentType<P>}>) => React$ComponentType<P>, +memo: <P>(component: React$ComponentType<P>, equal?: (P, P) => boolean) => React$ComponentType<P>, +useCallback: <T: (...args: $ReadOnlyArray<empty>) => mixed>(callback: T, inputs: ?$ReadOnlyArray<mixed>) => T, +useContext: <T>(context: React$Context<T>, observedBits: (void | number | boolean)) => T, +useEffect: (create: () => MaybeCleanUpFn, inputs: ?$ReadOnlyArray<mixed>) => void, +useImperativeHandle: <T>(ref: ?({current: (T | null)} | ((inst: (T | null)) => mixed)), create: () => T, inputs: ?$ReadOnlyArray<mixed>) => void, +useLayoutEffect: (create: () => MaybeCleanUpFn, inputs: ?$ReadOnlyArray<mixed>) => void, +useMemo: <T>(create: () => T, inputs: ?$ReadOnlyArray<mixed>) => T, +useReducer: ((<S, A>(reducer: (S, A) => S, initialState: S) => [S, Dispatch<A>]) & (<S, A>(reducer: (S, A) => S, initialState: S, init: void) => [S, Dispatch<A>]) & (<S, A, I>(reducer: (S, A) => S, initialArg: I, init: (I) => S) => [S, Dispatch<A>])), +useRef: <T>(initialValue: T) => {current: T}, +useState: <S>(initialState: ((() => S) | S)) => [S, ((((S) => S) | S)) => void], +version: string|}, +forwardRef: <Config, Instance>(render: (props: Config, ref: ({current: (null | Instance)} | (((null | Instance)) => mixed))) => React$Node) => React$AbstractComponent<Config, Instance>, +isValidElement: (element: any) => boolean, +lazy: <P>(component: () => Promise<{default: React$ComponentType<P>}>) => React$ComponentType<P>, +memo: <P>(component: React$ComponentType<P>, equal?: (P, P) => boolean) => React$ComponentType<P>, +useCallback: <T: (...args: $ReadOnlyArray<empty>) => mixed>(callback: T, inputs: ?$ReadOnlyArray<mixed>) => T, +useContext: <T>(context: React$Context<T>, observedBits: (void | number | boolean)) => T, +useDebugValue: (value: any) => void, +useEffect: (create: () => MaybeCleanUpFn, inputs: ?$ReadOnlyArray<mixed>) => void, +useImperativeHandle: <T>(ref: ?({current: (T | null)} | ((inst: (T | null)) => mixed)), create: () => T, inputs: ?$ReadOnlyArray<mixed>) => void, +useLayoutEffect: (create: () => MaybeCleanUpFn, inputs: ?$ReadOnlyArray<mixed>) => void, +useMemo: <T>(create: () => T, inputs: ?$ReadOnlyArray<mixed>) => T, +useReducer: ((<S, A>(reducer: (S, A) => S, initialState: S) => [S, Dispatch<A>]) & (<S, A>(reducer: (S, A) => S, initialState: S, init: void) => [S, Dispatch<A>]) & (<S, A, I>(reducer: (S, A) => S, initialArg: I, init: (I) => S) => [S, Dispatch<A>])), +useRef: <T>(initialValue: T) => {current: T}, +useState: <S>(initialState: ((() => S) | S)) => [S, ((((S) => S) | S)) => void], +version: string|}