shadows example

[PSteinhaus]

The shadows example has now been added, but is still incomplete.
To see how, just compare it to the one in ggez.

The blocks and text are rendered, but the lights and shadows aren't. Instead, one sees only a black background right now.

The shaders are already the same, so it's probably something in the code drawing it all, or even something faulty in the library itself...

Anyway, I perhaps didn't pay that much attention while porting it. If you should find anything, please speak up. Help here is very welcome.