docs: add some documentation for QUIC transport

docs/examples.echo_quic.rst

@@ -0,0 +1,43 @@
+QUIC Echo Demo
+==============
+
+This example demonstrates a simple ``echo`` protocol using **QUIC transport**.
+
+QUIC provides built-in TLS security and stream multiplexing over UDP, making it an excellent transport choice for libp2p applications.
+
+.. code-block:: console
+
+    $ python -m pip install libp2p
+    Collecting libp2p
+    ...
+    Successfully installed libp2p-x.x.x
+    $ echo-quic-demo
+    Run this from the same folder in another console:
+
+    echo-quic-demo -d /ip4/127.0.0.1/udp/8000/quic-v1/p2p/16Uiu2HAmAsbxRR1HiGJRNVPQLNMeNsBCsXT3rDjoYBQzgzNpM5mJ
+
+    Waiting for incoming connection...
+
+Copy the line that starts with ``echo-quic-demo -p 8001``, open a new terminal in the same
+folder and paste it in:
+
+.. code-block:: console
+
+    $ echo-quic-demo -d /ip4/127.0.0.1/udp/8000/quic-v1/p2p/16Uiu2HAmE3N7KauPTmHddYPsbMcBp2C6XAmprELX3YcFEN9iXiBu
+
+    I am 16Uiu2HAmE3N7KauPTmHddYPsbMcBp2C6XAmprELX3YcFEN9iXiBu
+    STARTING CLIENT CONNECTION PROCESS
+    CLIENT CONNECTED TO SERVER
+    Sent: hi, there!
+    Got: ECHO: hi, there!
+
+**Key differences from TCP Echo:**
+
+- Uses UDP instead of TCP: ``/udp/8000`` instead of ``/tcp/8000``
+- Includes QUIC protocol identifier: ``/quic-v1`` in the multiaddr
+- Built-in TLS security (no separate security transport needed)
+- Native stream multiplexing over a single QUIC connection
+
+.. literalinclude:: ../examples/echo/echo_quic.py
+    :language: python
+    :linenos:

docs/examples.rst

@@ -9,6 +9,7 @@ Examples
    examples.identify_push
    examples.chat
    examples.echo
+   examples.echo_quic
    examples.ping
    examples.pubsub
    examples.circuit_relay

docs/getting_started.rst

@@ -28,6 +28,11 @@ For Python, the most common transport is TCP. Here's how to set up a basic TCP t
 .. literalinclude:: ../examples/doc-examples/example_transport.py
    :language: python
 
+Also, QUIC is a modern transport protocol that provides built-in TLS security and stream multiplexing over UDP:
+
+.. literalinclude:: ../examples/doc-examples/example_quic_transport.py
+   :language: python
+
 Connection Encryption
 ^^^^^^^^^^^^^^^^^^^^^