Update readme to add back mention of doc folder, now that it exists
Update readme to add back mention of doc folder, now that it exists

vlj/TressFX,GPUOpen-Effects/TressFX,GPUOpen-Effects/TressFX,GPUOpen-Effects/TressFX,mrgreywater/TressFX,mrgreywater/TressFX,mrgreywater/TressFX,vlj/TressFX,vlj/TressFX