Observable
import type { Observable } from "https://raw.githubusercontent.com/surma/observables-with-streams/28c55be6d855780c677fd1f4ba975f4d3144891d/src/index.ts";An
Observable in the sense of ReactiveX.
The signature, however, does not match the one precedented in ReactiveX
and other languages. In its current incarnation, Observables are synonymous
with WHATWG ReadableStream.
type Observable<T> = ReadableStream<T>;