apps: DemoApp: Fully document the demo app

The demo app is of somewhat niche interest and is disabled by default
but arguable that makes it more important to document it fully since
this app is harder to find the many others.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

README.rst

@@ -145,6 +145,10 @@ simulator:
    :alt: Digital clock application running on the wasp-os simulator
    :width: 179
 
+.. image:: res/DemoApp.png
+   :alt: Simple always-on demo for showing off wasp-os at conferences and shows
+   :width: 179
+
 .. image:: res/HeartApp.png
    :alt: Heart rate application running on the wasp-os simulator
    :width: 179

docs/apps.rst

@@ -45,6 +45,8 @@ Applications
 
 .. automodule:: apps.calc
 
+.. automodule:: apps.demo
+
 .. automodule:: apps.flashlight
 
 .. automodule:: apps.haiku

wasp/apps/demo.py

@@ -8,6 +8,19 @@ This demo is simply an alternating sweep of the Pine64 and
 MicroPython logos. It cycles through a variety of colours
 and swaps between the logos every 5 images (so if you change
 anything make sure len(colors) is not a multiple of 5).
+
+.. figure:: res/DemoApp.png
+    :width: 179
+
+The demo also includes code to keep the devie awake making it
+suitable to run as an always-on application to demonstrate wasp-os at
+conferences and shows.
+
+.. note::
+
+    Due to it's niche purpose and relatively large size this app is not
+    included by default in the flash images. It must be separately installed
+    and enabled.
 """
 
 import wasp

wasp/boards/simulator/test_qa.py

@@ -3,7 +3,7 @@ import wasp
 import importlib
 import os
 
-EXCLUDE = ('Notifications', 'Template', 'Demo', 'Faces')
+EXCLUDE = ('Notifications', 'Template', 'Faces')
 
 def test_README(constructor):
     if constructor.NAME in EXCLUDE: