docs: Dual audio output example in audio.rst

Added an example multiplexing audio output using tee for local output and stream via icecast

docs/audio.rst

@@ -84,6 +84,13 @@ simultaneously. To use the Icecast output, do the following:
 
        [audio]
        output = audioresample ! audioconvert ! vorbisenc ! oggmux ! shout2send mount=mopidy ip=127.0.0.1 port=8000 password=hackme
+    
+   Example for MP3 streaming and local audio (multiple outputs):
+
+   .. code-block:: ini
+
+       [audio]
+       output = tee name=t ! queue ! audioresample ! autoaudiosink t. ! queue ! lamemp3enc ! shout2send mount=mopidy ip=127.0.0.1 port=8000 password=hackme
 
 Other advanced setups are also possible for outputs. Basically, anything you
 can use with the ``gst-launch-1.0`` command can be plugged into