Document fromPublisher + how to interop with FS2

README.md

@@ -432,12 +432,21 @@ If you have an `Observable[Future[A]]`, you can flatten it into `Observable[A]`
 
 A failed future results in an error (see [Error Handling](#error-handling)).
 
+#### Creating Observables from other Streaming APIs
+
+`EventStream.fromPublisher[A]` creates a stream that subscribes to a Reactive Streams [Publisher](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/concurrent/Flow.Publisher.html) and emits the values that it produces.
+
+`Publisher` is a common interface that is useful for interoperating between streaming APIs. For example, you can transform an [FS2](https://fs2.io/) `Stream[IO, A]` into an `EventStream[A]`.
+
+```scala
+import cats.effect.unsafe.implicits._ // implicit IORuntime
+EventStream.fromPublisher(fs2Stream.unsafeToPublisher())
+```
 
 #### `EventStream.fromJsPromise` and `Signal.fromJsPromise`
 
 Behave the same as `fromFuture` above, but accept `js.Promise` instead. Useful for integration with JS libraries and APIs.
 
-
 #### `EventStream.fromSeq`
 
 ```scala