Please add Canvas example

[goldenratio]

Hi,

Can you please add canvas example, like:

1. Draw some circles, rectangles
2. Display Bitmap sprite
3. Display animated bitmap

I tried playing around around with piston2d. I was not successful in exporting it to wasm. Thanks! :)

[mcamdenwm]

Sure thing. I've dug around a bit into this, but haven't yet created an example because of how complex OpenGL is.