feat(pipe): add piped operators

[mattpodwysocki]

Description:

Adds the pipe operator which allows us to compose functionality together for both Iterable and AsyncIterable.

An example of how it works is here:

import { AsyncIterableX as AsyncIterable } from 'ix/asynciterable';
import { filter } from 'ix/asynciterable/pipe/filter';
import { map } from 'ix/asynciterbale/pipe/map';

const source = AsyncIterable.of(1, 2, 3, 4, 5);
const piped = source.pipe(
  filter(async x => x % 2 === 0),
  map(async x => x * x)
);

for await (const item of piped) {
  console.log(`Item: ${item}`);
}

Related issue (if exists):

#46
#23

[jayphelps]

I think you'll want pipe to be an intrinsic method rather than an operator import you need to import explicitly. i.e. no need to do import 'ix/add/asynciterable-operators/pipe';. Otherwise you lose the benefit of libraries being able to use operators without adding them to the prototype, so they won't leak them to consumers of that library. rxjs provides it as an intrinsic

This might be confusing, so said another way: pipe should probably be included by default because otherwise libraries will have to add it to the prototype, which means then your app that consumes that library might accidentally depend on the fact that the library added it. Later, when the library decides they no longer need it, and stop adding it, your app breaks. 🎉