Add SampleApp slide with animating lightmapped objects & transparency

This is pulled out of the drawLitAtlas CL (may it someday land). It does nicely demonstrate animating normal mapped objects and normal maps combined with partially transparent diffuse textures.

It is a crude Asteroids game.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2026393005

TBR=reed@google.com

Review-Url: https://codereview.chromium.org/2026393005
4 files changed