Merge pull request 'Add an outline to the drawing zone' (#3) from dev into master

Reviewed-on: #3

guess_what_I_draw.py

@@ -82,9 +82,12 @@ class MyPaintWidget(Label):
         with self.canvas.before:
             Color(1,1,1, mode='rgb')
             self.bg = Rectangle(pos=self.pos, size=self.size)
+            Color(0,0,0, mode='rgb')
+            self.outline = Line(rectangle=(*self.pos, *self.size))
         def resize_bg(self, obj):
             self.bg.size = self.size
             self.bg.pos = self.pos
+            self.outline.rectangle=(*self.pos, *self.size)
         self.bind(size=resize_bg, pos=resize_bg)
 
         self._get_keyboard()