Add slang shader for shadow mapping and shadow mapping cascades sample

shaders/slang/shadowmappingcascade/debugshadowmap.slang

@@ -0,0 +1,29 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+[[vk::binding(1,0)]] Sampler2DArray shadowMapSampler;
+
+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, uniform float4 meshPosition, uniform uint cascadeIndex)
+{
+    float depth = shadowMapSampler.Sample(float3(input.UV, float(cascadeIndex))).r;
+	return float4(depth.xxx, 1.0);
+}