Multi-stream* example: add simple docs

To make it show up in the documentation.
It's also our only example showing SCTP.

Change-Id: Ib80ab869d9a6cbd370aa1a0c74772639e4393b37
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

examples/network/doc/src/multistreamclient.qdoc

@@ -0,0 +1,15 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \example multistreamclient
+    \title Multi-stream Client
+    \examplecategory {Networking}
+    \meta tags {network,sctp}
+    \ingroup examples-network
+    \brief Demonstrates how to use SCTP on the client side
+
+    This example demonstrates how to use SCTP, with multiple channels,
+    to interact with other clients through a server.
+    \image multi-stream-client-example.webp
+*/

examples/network/doc/src/multistreamserver.qdoc

@@ -0,0 +1,16 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \example multistreamserver
+    \title Multi-stream Server
+    \examplecategory {Networking}
+    \meta tags {network,sctp}
+    \ingroup examples-network
+    \brief Demonstrates how to use SCTP on the server side
+
+    This example demonstrates how to use SCTP, with multiple channels,
+    on the server side, receiving multiple connections and sending
+    messages to connected clients.
+    \image multi-stream-server-example.webp
+*/