update docs

Author: CedarGroveStudios

README.rst

@@ -63,7 +63,7 @@ Or the following command to update an existing version:
 Usage Example
 =============
 
-.. image:: https://github.com/CedarGroveStudios/CircuitPython_WaveViz/blob/main/media/waveviz_simpletest.png
+.. image:: https://github.com/CedarGroveStudios/CircuitPython_WaveViz/blob/main/media/waveviz_simpletest.jpeg
     :width: 400
 
 .. code-block:: python