Added HLSL shaders for ray tracing callable sample

Minor cleanup

data/shaders/hlsl/raytracingcallable/closesthit.rchit

@@ -0,0 +1,26 @@
+// Copyright 2021 Sascha Willems
+
+struct Attribute
+{
+  float2 attribs;
+};
+
+struct Payload
+{
+[[vk::location(0)]] float3 hitValue;
+};
+
+struct CallData
+{
+    float3 outColor;
+};
+
+[shader("closesthit")]
+void main(inout Payload p, in float3 attribs)
+{
+	// Execute the callable shader indexed by the current geometry being hit
+	// For our sample this means that the first callable shader in the SBT is invoked for the first triangle, the second callable shader for the second triangle, etc.
+	CallData callData;
+	CallShader(GeometryIndex(), callData);
+	p.hitValue = callData.outColor;
+}