add tonemapping shaders

shader/ToneMap/WhitePreservingLumaBasedReinhard.glsl

@@ -0,0 +1,9 @@
+vec3 ToneMapping(vec3 color)
+{
+	float white = 2.;
+	float luma = dot(color, vec3(0.2126, 0.7152, 0.0722));
+	float toneMappedLuma = luma * (1. + luma / (white*white)) / (1. + luma);
+	color *= toneMappedLuma / luma;
+
+	return linearTosRGB(color);
+}