examples: add a camera example (easy for testing the camera widget)

examples/camera/main.py

@@ -0,0 +1,25 @@
+#from kivy.logger import Logger
+#import logging
+#Logger.setLevel(logging.TRACE)
+from kivy.app import App
+from kivy.lang import Builder
+
+kv = '''
+BoxLayout:
+    orientation: 'vertical'
+    Camera:
+        id: camera
+        resolution: (640, 480)
+        play: False
+    ToggleButton:
+        text: 'Play'
+        on_press: camera.play = not camera.play
+        size_hint_y: None
+        height: '48dp'
+'''
+
+class TestCamera(App):
+    def build(self):
+        return Builder.load_string(kv)
+
+TestCamera().run()