StreamClass.prototype.intersperse<S>(separator: S): StreamClass<T | S, E>
Emits separator between every two elements — positional, so it also separates a value
from a passing failure.
await Stream.from([1, 2, 3]).intersperse(0).collect(); // [1, 0, 2, 0, 3]
separator: S
StreamClass<T | S, E>