Facade for `pipeThrough` options

[armanbilge]

• Change ReadableStream#pipeTo to return js.Promise[Unit] #639 (comment)
• https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/pipeThrough

scala-js-dom/dom/src/main/scala/org/scalajs/dom/ReadableStream.scala

Lines 59 to 62 in 49c89d2

	* //todo: determine the type of options
	*/
	def pipeThrough[U](pair: Any, // TODO js.Tuple2[WriteableStream[T], ReadableStream[U]]
	options: Any = js.native): ReadableStream[U] = js.native