[docs] Pictures for all the Examples (#5859)

* image

* plot resnet

* hyperparam

* fixup_pictures

* custom_direct

doc/examples/plot_pong_example.py

@@ -14,6 +14,10 @@ then be passed back to each Ray actor for more gradient calculation.
 This application is adapted, with minimal modifications, from
 Andrej Karpathy's `source code`_ (see the accompanying `blog post`_).
 
+.. image:: ../images/pong-arch.svg
+    :align: center
+
+
 To run the application, first install some dependencies.
 
 .. code-block:: bash