Change CullMode to none for sprites

[kaflu]

With CullMode::Back, a sprite image that is rotated in x,y plane won't display properly

[StarArawn]

I'm not sure this makes sense. I think instead making this optional seems like a better idea, but that would likely require significant changes. There are instances where you'd want to cull back faces to increase the speed of sprite rendering.

[StarArawn]

I opened a PR to address sprite flipping here:
#248
However I think we should still allow disabling of culling, but it should be optional.

[cart]

There are instances where you'd want to cull back faces to increase the speed of sprite rendering

Ooh i wasn't aware of this case. What instances?

[StarArawn]

Thinking about how culling works more I don't think it will speed up sprite rendering at all. 😳 There may be some cases where you only want sprites to render from one side though so I still think it should be optional. I think its fine if we disable the culling by default though.

[cart]

Cool I think this is good to go. Thanks!