doc: Readable unpipe on Writable error event

PR-URL: #18080
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/stream.md

@@ -323,6 +323,9 @@ The `'unpipe'` event is emitted when the [`stream.unpipe()`][] method is called
 on a [Readable][] stream, removing this [Writable][] from its set of
 destinations.
 
+This is also emitted in case this [Writable][] stream emits an error when a
+[Readable][] stream pipes into it.
+
 ```js
 const writer = getWritableStreamSomehow();
 const reader = getReadableStreamSomehow();
@@ -1496,6 +1499,9 @@ the callback and passing the error as the first argument. This will cause an
 on how the stream is being used.  Using the callback ensures consistent and
 predictable handling of errors.
 
+If a Readable stream pipes into a Writable stream when Writable emits an
+error, the Readable stream will be unpiped.
+
 ```js
 const { Writable } = require('stream');