Add a simple pygame demo

This allows to see patterns on a desktop without testing on Omnia.
However, this will display different color since the color profile for
the actual LEDs is not known (to me).

pygame_demo.py

@@ -0,0 +1,61 @@
+#!/bin/python3
+
+from omnia import leds
+import pygame
+
+# Re-implementation of LED in order to handle it ourself
+
+class MyLED(leds.LED):
+	def __init__(self, alias, order):
+		self.alias = alias
+		self._state = leds.LedState(
+			r = 0,
+			g = 0,
+			b = 0,
+			brightness = 0,
+			autonomous = False,
+			)
+		self.order = order
+		self.pgled = PGLED(order)
+	@property
+	def state(self):
+		return self._state
+	def set(self, state):
+		self._state = state
+		self.pgled.show(state)
+
+class PGLED:
+	"""This holds a pygame object to display the LED"""
+	SIZE = 30 # px incl. margins
+	BULB = 6 # px radius
+	def __init__(self, order):
+		self.order = order
+		self.rect = pygame.Rect(self.SIZE * self.order, 0, self.SIZE, self.SIZE)
+		self.surface = None
+
+	def set_surface(self, surf):
+		self.surface = surf
+
+	def show(self, state: leds.LedState):
+		# Fill with black
+		black = pygame.Color(0,0,0)
+		pygame.draw.rect(self.surface, black, self.rect)
+		# Draw the circle with required color
+		# And respect the brightness
+		color = pygame.Color(state.r * state.brightness//255, state.g * state.brightness//255, state.b * state.brightness//255)
+		pygame.draw.circle(self.surface, color, self.rect.center, self.BULB)
+		pygame.display.flip()
+
+my_strip = leds.LedStrip([MyLED(al, i) for i, al in enumerate(leds.omnia_led_order)])
+
+w = PGLED.SIZE * len(my_strip)
+h = PGLED.SIZE
+
+pygame.init()
+pygame.mixer.quit()
+display = pygame.display.set_mode((w, h))
+display.fill((0,0,0))
+pygame.display.flip()
+
+for led in my_strip:
+	led.pgled.set_surface(display)