external
import { external } from "https://raw.githubusercontent.com/surma/observables-with-streams/28c55be6d855780c677fd1f4ba975f4d3144891d/src/sources/external.ts";Utility function to create new observables from external sources.
Returns an object with two values: the new observable, and a next function
which will emit a value to observable when called.
Calling next with EOF will indicate there are no more values to emit.
function external<T>();