Add slang shader for shadow mapping and shadow mapping cascades sample

shaders/slang/shadowmapping/quad.slang

@@ -0,0 +1,48 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct UBO
+{
+	float4x4 projection;
+	float4x4 view;
+	float4x4 model;
+	float4x4 lightSpace;
+	float4 lightPos;
+	float zNear;
+	float zFar;
+};
+ConstantBuffer<UBO> ubo;
+Sampler2D samplerColor;
+
+float LinearizeDepth(float depth)
+{
+  float n = ubo.zNear;
+  float f = ubo.zFar;
+  float z = depth;
+  return (2.0 * n) / (f + n - z * (f - n));
+}
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float2 UV;
+};
+
+[shader("vertex")]
+VSOutput vertexMain(uint VertexIndex: SV_VertexID)
+{
+    VSOutput output;
+    output.UV = float2((VertexIndex << 1) & 2, VertexIndex & 2);
+    output.Pos = float4(output.UV * 2.0f - 1.0f, 0.0f, 1.0f);
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    float depth = samplerColor.Sample(input.UV).r;
+    return float4((1.0 - LinearizeDepth(depth)).xxx, 1.0);
+}