message: set blend constant to black to match original ggez behaviour
diff: @@ -163,7 +163,7 @@ impl<'a> InternalCanvas<'a> {
  (arenas, pass)
  };
  - pass.set_blend_constant(wgpu::Color::WHITE);
  + pass.set_blend_constant(wgpu::Color::BLACK);
  let size = gfx.window.inner_size();
  let screen_coords = Rect {
  