Improper drawing in shapes_top_down_lights example

[stefandd]

Currently, the example only renders when the variable lights_dirty is true. However, this makes the example hang since keyboard and mouse functionality are frame-based and refreshed only when a drawing is performed. You'd need to have at least some R.begin_drawing .. R.end_drawing in every loop cycle..

[sol-vin]

Hey, thanks so much. I honestly didn't know what was wrong with this one and totally forgot about it. Fixed with latest commit.

[stefandd]

Great. It is fixed now -- thanks for your work!