true if T is an AnyFunction, otherwise false.
An AnyFunction is defined as a function type that accepts any arguments and returns any value.
IsAnyFunction<() => void>; // true (matches AnyFunction)
IsAnyFunction<(x: number) => string>; // true (matches AnyFunction)
IsAnyFunction<string>; // false (string is not a function type)
Type utility that checks if a given type
Tis anAnyFunction(any function type).