Added slang shaders for deferred shadows sample

shaders/slang/deferredshadows/shadow.slang

@@ -0,0 +1,57 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+#define LIGHT_COUNT 3
+
+struct VSInput
+{
+    float4 Pos;
+}
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+	int InstanceIndex;
+};
+
+struct GSOutput
+{
+	float4 Pos : SV_POSITION;
+	int Layer : SV_RenderTargetArrayIndex;
+};
+
+struct UBO
+{
+    float4x4 mvp[LIGHT_COUNT];
+    float4 instancePos[3];
+};
+ConstantBuffer<UBO> ubo;
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input, uint InstanceIndex: SV_InstanceID)
+{
+    VSOutput output;
+    output.InstanceIndex = InstanceIndex;
+    output.Pos = input.Pos;
+    return output;
+}
+
+[shader("geometry")]
+[maxvertexcount(3)]
+[instance(3)]
+void geometryMain(triangle VSOutput input[3], uint InvocationID : SV_GSInstanceID, inout TriangleStream<GSOutput> outStream)
+{
+	float4 instancedPos = ubo.instancePos[input[0].InstanceIndex];
+	for (int i = 0; i < 3; i++)
+	{
+		float4 tmpPos = input[i].Pos + instancedPos;
+		GSOutput output;
+		output.Pos = mul(ubo.mvp[InvocationID], tmpPos);
+		output.Layer = InvocationID;
+		outStream.Append( output );
+	}
+	outStream.RestartStrip();
+}