doc: document http2 network error behaviour

Fixes: #21836

PR-URL: #21861
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>

doc/api/http2.md

@@ -271,12 +271,17 @@ server.on('stream', (stream, headers) => {
     'content-type': 'text/html',
     ':status': 200
   });
+  stream.on('error', (error) => console.error(error));
   stream.end('<h1>Hello World</h1>');
 });
 
 server.listen(80);
 ```
 
+Even though HTTP/2 streams and network sockets are not in a 1:1 correspondence,
+a network error will destroy each individual stream and must be handled on the
+stream level, as shown above.
+
 #### Event: 'timeout'
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